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Incadelphys antiquus Marshall & Muizon, 1988 HOLOTYPE. — YPFB Pal 6151, partial upper and lower jaws of the same juvenile specimen including the left maxilla with base of P1, P2, dP3, unerupted P3, M1-M3 (M3 erupting and missing tip of protocone); the right maxilla with dP3 unerupted P3, M1-M3 (M3 erupting); the right mandibular ramus with p1, p2, dp3, unerupted p3; m1-2, talonid of m3, unerupted m4; the left mandibular ramus with talonid of dp3, m1-2, m3 broken, m4 unerupted (Fig. 2) EMENDED DIAGNOSIS. — Dental formula I5/i4, C/c, P3/p3; M4/ m4; skull slightly smaller than Pucadelphys but distinctly larger than Szalinia; approaching the size of the extant didelphid Thylamys, proportions of the rostrum approaching those of Pucadelphys with the apex more slender; palatal vacuities absent. Incadelphys antiquus differs from Pucadelphyidae in the following features: occurrence of a distinct lacrimal-nasal contact; extremely narrow and blade-like upper premolars, with weaker labial and lingual posterocingula (in pucadelphyids upper premolars are wider with thick labial and lingual posterocingula); upper molar smaller and more gracile; M1 strongly asymmetrical; distolabial angle of M1 conspicuously extended distolingually with angle between labial edge of tooth and postmetacrista varying from 34° to 37° (in pucadelphyids the angle vary from 49° to 62°; mean = 51.4°); protocone mesiodistally shorter; mesiodistal constriction (i.e. shortening) at lingual base of para-metacone more pronounced, especially on M3, (in pucadelphyids constriction is weak to absent); posterolingual inflation of protocone absent or faint (in pucadelphyids posterolingual inflation present); centrocrista weakly V-shaped (in pucadelphyids V-shaped centrocrista is generally conspicuous); anterior stylar shelf on M1 narrower; stylar cusp C absent on M3, absent or small on M1-M2 (in pucadelphyids stylar cusp C is generally present in M1- M3); when present, stylar cusp C much smaller than B and D (in pucadelphyids stylar cusp C is generally subequal to slightly smaller than D); distolabial angle of M1 extending distolabially to a greater extent, with angle between postmetacrista and lingual edge of the tooth smaller; ectoflexus totally absent on M1 (present in pucadelphyids) and shallower on M2-M3 (deep in pucadelphyids); ventral edge of dentary less convex; coronoid process distinctly narrower at apex and not recurved posteriorly (in other words posterior edge of process straight) (in pucadelphyids apex of coronoid process is strongly recurved posteriorly); retromolar space longer (almost as long as m4) (in pucadelphyids it is generally as long as or shorter than talonid of m4); lower molars proportionally narrower; entoconid proportionally larger, slightly higher as compared to hypoconid (in pucadelphyids the entoconid is approximatively as high as the hypoconid). Incadelphys antiquus differs from Aenigmadelphys archeri in that the paracone is slightly smaller in height and volume than the metacone (reversed in A. archeri); paraconule subequal to metaconule (in A.archeri paraconule is larger than metaconule); ectoflexus absent on M1 (present and shallow in A. archeri); anterior stylar shelf narrower than posterior (in A. archeri the anterior stylar shelf is wider than the posterior on the holotype only [an M3], but it is narrower on OMNH 23460, [an M3 lacking the protocone], OMNH 20120 [an M2], and OMNH 22898 [an M1]); stylar cusp B and D subequal in size (in A. archeri stylar cusp B is consistently larger than D); stylar cusp C absent on M3 (in A. archeri it is small but distinct); trigonid lower as compared to talonid; paraconid distinctly smaller than metaconid (in A. archeri paraconid is subequal in size to metaconid or slightly smaller). HYPODIGM. — The holotype; MHNC 13906, anterior half of a skull including both premaxillae, maxillae, nasals, lacrimals, anterior part of the frontals, anterior part of the jugals, right I3-M4, left I1-M4 (crown of I1-2 broken at base; labial edge of stylar shelf of M3-4 missing); left dentary (missing coronoid process) with i1-m4; right dentary with i2-m4 (labial edge of protoconid of m1- m3 abraded, associated to the skull, the specimen also includes seven caudal vertebrae, three metacarpals and three metatarsals; MHNC 13947, a partial maxilla with M1-M3; MHNC 8270, a left mandible, with c-m3 and alveoli of m4 (on molars lingual edge of para- and metaconid is scratched), MHNC 13933, a left M2, MHNC 13935, a left M2. GEOLOGICAL SETTING AND AGE. — All the specimens of Incadelphys antiquus are from beds of the Santa Lucía Formation at Tiupampa and have been discovered in the locality called “the Quarry” by Gayet et al. (1992) and Marshall & Muizon (1995). As discussed by Gelfo et al. (2009), Muizon et al. (2015, 2018), Muizon & Ladevèze (2020), the age of the Tiupampa beds is regarded as early Danian in age (c. 65 Ma) contra Zimicz et al. (2020). COMPARATIVE DESCRIPTION The new specimen of Incadelphys antiquus described here is an anterior part of a skull including the upper tooth rows and the palate, and both dentaries (Fig. 3). The specimen has suffered some distortion and the left maxilla has been displaced dorsally. In spite of this distortion, it seems that the width of the rostrum has not been strongly affected. The specimen includes the premaxillae, the maxillae, the lacrimals, the nasals, the anterior part of the frontals and jugals. The dentaries are almost complete with all their teeth. However, during collection of the specimen, the lateral side of the left tooth rows have been damaged; on upper teeth, the posterolabial angle of M3 and the labial edge of the stylar shelf of M4 have been destroyed. On the lower teeth, the labial edge of the protoconid and hypoconid of m1-m3 have been scratched during the collection of the specimen. Dentition The dental formula is the plesiomorphic pattern for metatherians: I5/i4, C/c, P3/p3, M4/m4 (Kielan-Jaworowska et al. 2004). The upper dentition will be described first, followed by the lower dentition. Upper dentition Upper incisors (Figs 4; 5). the crowns of I1 and I2 are missing and the roots of these teeth are preserved only on the left premaxilla. I1 has a slightly smaller diameter than I2. This condition contrasts with that of extant didelphids and Andinodelphys, in which I1 is distinctly larger than I2. In contrast, it resembles the condition observed in the only Pucadelphys specimens that preserve the I1s (YPFB Pal 6105, the holotype, and MHNC 8378, referred to females by Ladevèze et al. 2011). A small diastema is present between I1 and I2. The diastema is approximately as long as the diameter of I1. A similar condition is present in some specimens of Pucadelphys (MHNC 8378) and in didelphids but is absent in Andinodelphys. The crowns of the other incisors are preserved. They are subequal in size to I2, with I5 being slightly smaller. Their crown is peg-like. It is slightly compressed labiolingually on I3 and I4 and roughly conical on I5. Upper Canine (Figs 4; 5). The upper canine is large and sharp and is approximately three times as high as the P3. It is larger than in Marmosa, in which it is twice as high as P3, and Thylamys, in which it is less than twice the high of P3. It is similar in height to the canines of Didelphis and Caluromys, in which they are approximately three times (or more) as high as the P3. Among the Tiupampa metatherians, the canine of Incadelphys is similar in relative height to those of Andinodelphys and specimens interpreted by Ladevèze et al. (2011) as males of Pucadelphys (e.g., MHNC 8266, 8377, 8382). In contrast, it is clearly higher than the canines of the specimens referred to females of Pucadelphys by these authors (e.g., MHNC 8376, 8378), in which the canine height is less than twice that of P3. As in all didelphids and pucadelphyids, the upper canines of Incadelphys are transversely compressed being approximately twice as long as wide. As in didelphids and pucadelphyids, they are strongly curved posteriorly. The upper canine of Incadelphys is slightly procumbent as indicated by the position of the apex of the tooth, which is ventral to the anterior edge of the crown base. Upper premolars (Figs 4; 5). The three premolars are doublerooted and distinctly increase in size from P1 to P3. As observed on the right side of the skull, the increase in size is progressive. In other words, the increase in size between P1 and P2 is similar to that between P2 and P3. This condition differs from that observed in Andinodelphys, in which a great increase in size is observed between P1 and P2 and a smaller increase exists between P2 and P3. A small diastema is present between P1 and P2, and a smaller one between P2 and P3. P1 and P2 are extremely narrow transversely and blade-like, whereas P3 is slightly wider (Table 1). The blade-like morphology of the P1-P2 is not observed in any of the other Tiupampa metatherians. As shown on Table 2 the ratio W/L for the P2 of Incadelphys is 0.31 (three measurements), 0.45 for Andinodelphys (seven measurements), and for Pucadelphys 0.56 (ten measurements). Therefore, the relative width (as compared to length) of the P2 of Incadelphys is 31% smaller than in Andinodelphys and 45% smaller than in Pucadelphys. Given these results, the blade-like morphology of the anterior upper premolars of Incadelphys is regarded as a significant characteristic of the genus. P1 is triangular in lateral view. It is slightly asymmetrical, with its apex located below the anterior root. It is less asymmetrical than in Andinodelphys, in which the apex of P1 is ventral to the posterior edge of the posterior root. The P1 of Incadelphys has no posterior accessory cusp, nor cingulum. Its anterior root contacts the posterior edge of the canine, but it is not closely appressed against it, thus differing from the condition of Andinodelphys. P2 is less asymmetrical than P1 and its apex is ventral to the inter-alveolar septum. Similarly to P1, it is as long as high. Its anterior and posterior edges are straight. The tooth bears a small cingulum at the anterior edge of the crown, which forms a hint of an anterior basal cuspule. The cingulum extends on the lingual aspect of the crown, below the anterior root. Posteriorly a conspicuous basal cusp is present. P3 is more robust and more inflated than P2. Its anterior edge is slightly convex and its posterior edge slightly concave. The apex of the crown is located below the anterior edge of the posterior root. The anterior border of the crown is rounded, whereas the posterior edge becomes thinner, sharp, and crest-like. The lateral edges of the crown, in this region, are distinctly concave. The anterior cingulum is strong (as compared to that of P2). It extends on the mesiolabial and mesiolingual angles of the crown but remains at the level of the anterior root. Posteriorly, the basal accessory cusp is well developed. It imbricates in the mesiolingual angle of M1 with the stylar cusp A. Labial and lingual to the basal cusp are small cingular shelves. Upper molars (Figs 4; 5). The description of the upper molars will consider the five available specimens: the holotype YPFB Pal 6251, which includes both maxillae and mandibles of a subadult individual (i.e. upper M4 are missing and m4 are unerupted); MHNC 13906 (which preserves complete maxillae and mandibles and 13931 a partial maxilla with M1-3). M1 is relatively different from the other molars and will be treated first. M2-M3, which have a more typical morphology as compared to most of the other Tiupampan metatherians will be described jointly. M4, which strongly differs from the preceding molar, as in most metatherians, will be studied next. M1 is a distinctive tooth of Incadelphys in the distolabial extension of its metastylar angle. As a consequence, the labial edge of M1 is much longer than on the other molars (Table 1). The anterior edge is shorter than on the posterior molars, and the tooth is longer than wide (1.56 mm vs 1.54mm; mean of five measurements, seeTable 1), a condition that contrasts with that of Andinodelphys, Pucadelphys, and Mizquedelphys. A condition of the M1 similar to that of Incadelphys is observed in the Campanian genus Aenigmadelphys of Utah. Table 3 compares the angle between the line joining stylar cusps D and E and the postmetacrista. Because the postmetacrista is often curved, and because the posterolabial part of the crista is relatively straight, the latter has been used for the measurement. As observed inTable 2, the mean of the angle obtained for pucadelphyids (53.2°) is approximately 48% and 32% greater than the angle of Incadelphys and Aenigmadelphys respectively. Because of this difficulty of measurement, the value of the angle obtained is certainly somewhat imprecise. However, because of the great difference observed, this result is probably significant. As a consequence of the posterolabial extension of the M1, its mesial edge is distinctly shorter than its labial edge. A similar condition is also observed in Aenigmadelphys. Marmosopsis from the early Eocene of Itaboraí, clearly ranges close to Incadelphys, whereas Monodelphis and Thylamys are closer to pucadelphyids than to Incadelphys and Aenigmadelphys. The protocone of M1 is relatively massive, being mesiodistally longer than wide on the three specimens. It is roughly symmetrical mesiodistally and does not present the distolingual inflation observed in didelphids and pucadelphyids. The mesial and distal bases of the protocone are smooth and bear no cingulum. Para- and metaconules are well-developed (almost as large as stylar cusps B and D). From the paraconule, a conspicuous paracingulum (i.e. labial extension of the preparaconular crista) extends up to stylar cusp A. Distally, the metaconule abuts the distal base of metacone but no metacingulum (i.e. labial extension of the postmetaconular crista) is present. The paracone is slightly smaller in height and volume than the metacone. Both cusps are widely separated at base, as in didelphids and pucadelphyids. A deep trigon basin is bordered by the distolingual aspect of the paracone, the mesiolingual aspect of the metacone and the labial aspect of the protocone. The lingual aspect of the para- and metacone is strongly convex, whereas their labial aspect is flat to slightly concave. As a consequence, the cusps are triangular in section and the pre- and post- paracristae and pre- and post-metacristae are shifted labially, forming the lingual wall of the stylar shelf. The junction of the postparacrista and premetacrista (i.e. the median point of the centrocrista) is displaced labially, and the centrocrista is slightly V-shaped in occlusal view. This condition, which is present in Aenigmadelphys, didelphids, and pucadelphyids, differs from that observed, for instance, in Kokopellia, alphadontids, peradectids, and sparassodonts, in which the labial and lingual aspects of the para- and metacone are markedly convex (generally slightly less convex labially than lingually), the pre- and post- paracristae and pre-and post-metacristae are in a median position relative to the para- and metacone and therefore the centrocrista is straight. The stylar shelf of Incadelphys is narrow, being almost absent anteriorly since the stylar cusp B is almost connate to the paracone to which it is connected by a very short preparacrista. The stylar cusp A is smaller than B but conspicuous. It surrounds posterolabially and imbricates with the posterobasal cusp of P3. Stylar cusp B and D are large and subequal in size, but variation exists. In MHNC 13906, StB is slightly smaller than StD, whereas in MHNC 13931 StB is slightly larger than StD; these cusps are subequal in the holotype. Stylar cusp B is conical, whereas stylar cusp D is transversely compressed. Between StB and StD, a small stylar cusp C is present in the holotype and MHNC 13906. Stylar cusp C is lacking in MHNC 13931. Stylar cusp E is indistinguishable. The labial edge of M1 is straight and features no ectoflexus. M2 and M3 are conspicuously wider than long. They differ from M 1 in the protocone, which is approximately as long as wide on M2 and clearly wider than long on M3. The stylar shelf is wider than on M1, especially its anterior part. As a consequence, the stylar cusp B is well separated from the paracone, and the preparacrista is as long as the postparacrista on M2 and slightly longer on M3. The preparacrista contacts stylar cusp B on its anterior edge, almost between cusp B and A on MHNC 13906. Stylar cusp C is small to absent and stylar cusp D is well developed but smaller than B. On the labial edge of M2 is a small ectoflexus (rather a notch) between stylar cusps B and C. On M3, the ectoflexus is deeper and located between stylar cusps C and D. From M1 to M3, at the distolabial corner of the tooth, the angle between the labial edge and the postmetacrista increases and, as a consequence, the postmetacrista is more transverse posteriorly. M2-M3 of Incadelphys strongly resemble those of Aenigmadelphys, from which they differ however in the latter being transversely wider and mesiodistally shorter (see comparison below p. 000). Furthermore, the M2-M3 of Aenigmadelphys have a slightly wider stylar shelf. On M4, the protocone is shorter mesiodistally than on the anterior molars and the metacone is greatly reduced compared to that of the anterior molars, being significantly smaller than the paracone. The anterior stylar shelf is wider and the preparacrista is longer than on M2-M3. The posterior stylar shelf is very narrow but still present labial to the metacone. The M4 of Incadelphys differs from that of Aenigmadelphys in the latter being mesiodistally shorter, transversely wider with a longer preparacrista, and in the posterior stylar shelf being virtually absent. Lower dentition Lower incisors (Figs 6; 7). The four incisors are preserved on the left dentary, but i1 is missing part of its crown. In the description below, we follow the interpretation of Hershkovitz (1982, 1995), that the four lower incisors of metatherians are serially homologous to i2-i5. On the right dentary i2-i4 are preserved but i5 is missing its crown. In size, the crown of i2 is smaller than that of i3 but larger than i4; i5 is the smallest of the four incisors. The crowns are peg-like but slightly spatulate, being wider than high. The apex of the crown of i2 is roughly semicircular in labial or lingual view; that of i3 is lanceolate with a carina on its lingual aspect; that of i4 is similar to i1 but smaller and that of i5 is also somewhat lanceolate. The i3 is distinctly staggered as indicated by the buttress visible on the anterolabial edge of the dentary just ventral to the labial aspect of the tooth and by the posterior shift of its root observable lingually on MHNC 13906. Lower canine (Figs 6; 7). The lower canine is a large tooth, although consistently smaller than the upper canine. It is pointed at its apex and curved (from the alveolar border) dorsally but not posteriorly. In other words, the apex of the tooth does not overhang the, Published as part of Muizon, Christian de & Ladevèze, Sandrine, 2022, New material of Incadelphys antiquus (Pucadelphyda, Metatheria, Mammalia) from the early Palaeocene of Bolivia reveals phylogenetic affinities with enigmatic North and South American metatherians, pp. 609-643 in Geodiversitas 44 (22) on pages 613-630, DOI: 10.5252/geodiversitas2022v44a22, http://zenodo.org/record/6795405, {"references":["MARSHALL L. G. & MUIZON C. DE 1988. - The dawn of the age of mammals in South America. National Geographic Research 4 (1): 23 - 55.","GAYET M., MARSHALL L. G. & SEMPERE T. 1992. - The Mesozoic and Palaeocene vertebrates of Bolivia and their stratigraphic context: a review. Revista Tecnica de YPFB 12 (3 - 4): 393 - 433.","MARSHALL L. G. & MUIZON C. DE 1995. - Part II: The skull, in MUIZON C. 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Muizon, Christian de, Ladevèze, Sandrine (2022): New material of Incadelphys antiquus (Pucadelphyda, Metatheria, Mammalia) from the early Palaeocene of Bolivia reveals phylogenetic affinities with enigmatic North and South American metatherians. Geodiversitas 44 (22): 609-643, DOI: 10.5252/geodiversitas2022v44a22

Incadelphys antiquus Marshall & Muizon, 1988 HOLOTYPE. — YPFB Pal 6151, partial upper and lower jaws of the same juvenile specimen including the left maxilla with base of P1, P2, dP3, unerupted P3, M1-M3 (M3 erupting and missing tip of protocone); the right maxilla with dP3 unerupted P3, M1-M3 (M3 erupting); the right mandibular ramus with p1, p2, dp3, unerupted p3; m1-2, talonid of m3, unerupted m4; the left mandibular ramus with talonid of dp3, m1-2, m3 broken, m4 unerupted (Fig. 2) EMENDED DIAGNOSIS. — Dental formula I5/i4, C/c, P3/p3; M4/ m4; skull slightly smaller than Pucadelphys but distinctly larger than Szalinia; approaching the size of the extant didelphid Thylamys, proportions of the rostrum approaching those of Pucadelphys with the apex more slender; palatal vacuities absent. Incadelphys antiquus differs from Pucadelphyidae in the following features: occurrence of a distinct lacrimal-nasal contact; extremely narrow and blade-like upper premolars, with weaker labial and lingual posterocingula (in pucadelphyids upper premolars are wider with thick labial and lingual posterocingula); upper molar smaller and more gracile; M1 strongly asymmetrical; distolabial angle of M1 conspicuously extended distolingually with angle between labial edge of tooth and postmetacrista varying from 34° to 37° (in pucadelphyids the angle vary from 49° to 62°; mean = 51.4°); protocone mesiodistally shorter; mesiodistal constriction (i.e. shortening) at lingual base of para-metacone more pronounced, especially on M3, (in pucadelphyids constriction is weak to absent); posterolingual inflation of protocone absent or faint (in pucadelphyids posterolingual inflation present); centrocrista weakly V-shaped (in pucadelphyids V-shaped centrocrista is generally conspicuous); anterior stylar shelf on M1 narrower; stylar cusp C absent on M3, absent or small on M1-M2 (in pucadelphyids stylar cusp C is generally present in M1- M3); when present, stylar cusp C much smaller than B and D (in pucadelphyids stylar cusp C is generally subequal to slightly smaller than D); distolabial angle of M1 extending distolabially to a greater extent, with angle between postmetacrista and lingual edge of the tooth smaller; ectoflexus totally absent on M1 (present in pucadelphyids) and shallower on M2-M3 (deep in pucadelphyids); ventral edge of dentary less convex; coronoid process distinctly narrower at apex and not recurved posteriorly (in other words posterior edge of process straight) (in pucadelphyids apex of coronoid process is strongly recurved posteriorly); retromolar space longer (almost as long as m4) (in pucadelphyids it is generally as long as or shorter than talonid of m4); lower molars proportionally narrower; entoconid proportionally larger, slightly higher as compared to hypoconid (in pucadelphyids the entoconid is approximatively as high as the hypoconid). Incadelphys antiquus differs from Aenigmadelphys archeri in that the paracone is slightly smaller in height and volume than the metacone (reversed in A. archeri); paraconule subequal to metaconule (in A.archeri paraconule is larger than metaconule); ectoflexus absent on M1 (present and shallow in A. archeri); anterior stylar shelf narrower than posterior (in A. archeri the anterior stylar shelf is wider than the posterior on the holotype only [an M3], but it is narrower on OMNH 23460, [an M3 lacking the protocone], OMNH 20120 [an M2], and OMNH 22898 [an M1]); stylar cusp B and D subequal in size (in A. archeri stylar cusp B is consistently larger than D); stylar cusp C absent on M3 (in A. archeri it is small but distinct); trigonid lower as compared to talonid; paraconid distinctly smaller than metaconid (in A. archeri paraconid is subequal in size to metaconid or slightly smaller). HYPODIGM. — The holotype; MHNC 13906, anterior half of a skull including both premaxillae, maxillae, nasals, lacrimals, anterior part of the frontals, anterior part of the jugals, right I3-M4, left I1-M4 (crown of I1-2 broken at base; labial edge of stylar shelf of M3-4 missing); left dentary (missing coronoid process) with i1-m4; right dentary with i2-m4 (labial edge of protoconid of m1- m3 abraded, associated to the skull, the specimen also includes seven caudal vertebrae, three metacarpals and three metatarsals; MHNC 13947, a partial maxilla with M1-M3; MHNC 8270, a left mandible, with c-m3 and alveoli of m4 (on molars lingual edge of para- and metaconid is scratched), MHNC 13933, a left M2, MHNC 13935, a left M2. GEOLOGICAL SETTING AND AGE. — All the specimens of Incadelphys antiquus are from beds of the Santa Lucía Formation at Tiupampa and have been discovered in the locality called “the Quarry” by Gayet et al. (1992) and Marshall & Muizon (1995). As discussed by Gelfo et al. (2009), Muizon et al. (2015, 2018), Muizon & Ladevèze (2020), the age of the Tiupampa beds is regarded as early Danian in age (c. 65 Ma) contra Zimicz et al. (2020). COMPARATIVE DESCRIPTION The new specimen of Incadelphys antiquus described here is an anterior part of a skull including the upper tooth rows and the palate, and both dentaries (Fig. 3). The specimen has suffered some distortion and the left maxilla has been displaced dorsally. In spite of this distortion, it seems that the width of the rostrum has not been strongly affected. The specimen includes the premaxillae, the maxillae, the lacrimals, the nasals, the anterior part of the frontals and jugals. The dentaries are almost complete with all their teeth. However, during collection of the specimen, the lateral side of the left tooth rows have been damaged; on upper teeth, the posterolabial angle of M3 and the labial edge of the stylar shelf of M4 have been destroyed. On the lower teeth, the labial edge of the protoconid and hypoconid of m1-m3 have been scratched during the collection of the specimen. Dentition The dental formula is the plesiomorphic pattern for metatherians: I5/i4, C/c, P3/p3, M4/m4 (Kielan-Jaworowska et al. 2004). The upper dentition will be described first, followed by the lower dentition. Upper dentition Upper incisors (Figs 4; 5). the crowns of I1 and I2 are missing and the roots of these teeth are preserved only on the left premaxilla. I1 has a slightly smaller diameter than I2. This condition contrasts with that of extant didelphids and Andinodelphys, in which I1 is distinctly larger than I2. In contrast, it resembles the condition observed in the only Pucadelphys specimens that preserve the I1s (YPFB Pal 6105, the holotype, and MHNC 8378, referred to females by Ladevèze et al. 2011). A small diastema is present between I1 and I2. The diastema is approximately as long as the diameter of I1. A similar condition is present in some specimens of Pucadelphys (MHNC 8378) and in didelphids but is absent in Andinodelphys. The crowns of the other incisors are preserved. They are subequal in size to I2, with I5 being slightly smaller. Their crown is peg-like. It is slightly compressed labiolingually on I3 and I4 and roughly conical on I5. Upper Canine (Figs 4; 5). The upper canine is large and sharp and is approximately three times as high as the P3. It is larger than in Marmosa, in which it is twice as high as P3, and Thylamys, in which it is less than twice the high of P3. It is similar in height to the canines of Didelphis and Caluromys, in which they are approximately three times (or more) as high as the P3. Among the Tiupampa metatherians, the canine of Incadelphys is similar in relative height to those of Andinodelphys and specimens interpreted by Ladevèze et al. (2011) as males of Pucadelphys (e.g., MHNC 8266, 8377, 8382). In contrast, it is clearly higher than the canines of the specimens referred to females of Pucadelphys by these authors (e.g., MHNC 8376, 8378), in which the canine height is less than twice that of P3. As in all didelphids and pucadelphyids, the upper canines of Incadelphys are transversely compressed being approximately twice as long as wide. As in didelphids and pucadelphyids, they are strongly curved posteriorly. The upper canine of Incadelphys is slightly procumbent as indicated by the position of the apex of the tooth, which is ventral to the anterior edge of the crown base. Upper premolars (Figs 4; 5). The three premolars are doublerooted and distinctly increase in size from P1 to P3. As observed on the right side of the skull, the increase in size is progressive. In other words, the increase in size between P1 and P2 is similar to that between P2 and P3. This condition differs from that observed in Andinodelphys, in which a great increase in size is observed between P1 and P2 and a smaller increase exists between P2 and P3. A small diastema is present between P1 and P2, and a smaller one between P2 and P3. P1 and P2 are extremely narrow transversely and blade-like, whereas P3 is slightly wider (Table 1). The blade-like morphology of the P1-P2 is not observed in any of the other Tiupampa metatherians. As shown on Table 2 the ratio W/L for the P2 of Incadelphys is 0.31 (three measurements), 0.45 for Andinodelphys (seven measurements), and for Pucadelphys 0.56 (ten measurements). Therefore, the relative width (as compared to length) of the P2 of Incadelphys is 31% smaller than in Andinodelphys and 45% smaller than in Pucadelphys. Given these results, the blade-like morphology of the anterior upper premolars of Incadelphys is regarded as a significant characteristic of the genus. P1 is triangular in lateral view. It is slightly asymmetrical, with its apex located below the anterior root. It is less asymmetrical than in Andinodelphys, in which the apex of P1 is ventral to the posterior edge of the posterior root. The P1 of Incadelphys has no posterior accessory cusp, nor cingulum. Its anterior root contacts the posterior edge of the canine, but it is not closely appressed against it, thus differing from the condition of Andinodelphys. P2 is less asymmetrical than P1 and its apex is ventral to the inter-alveolar septum. Similarly to P1, it is as long as high. Its anterior and posterior edges are straight. The tooth bears a small cingulum at the anterior edge of the crown, which forms a hint of an anterior basal cuspule. The cingulum extends on the lingual aspect of the crown, below the anterior root. Posteriorly a conspicuous basal cusp is present. P3 is more robust and more inflated than P2. Its anterior edge is slightly convex and its posterior edge slightly concave. The apex of the crown is located below the anterior edge of the posterior root. The anterior border of the crown is rounded, whereas the posterior edge becomes thinner, sharp, and crest-like. The lateral edges of the crown, in this region, are distinctly concave. The anterior cingulum is strong (as compared to that of P2). It extends on the mesiolabial and mesiolingual angles of the crown but remains at the level of the anterior root. Posteriorly, the basal accessory cusp is well developed. It imbricates in the mesiolingual angle of M1 with the stylar cusp A. Labial and lingual to the basal cusp are small cingular shelves. Upper molars (Figs 4; 5). The description of the upper molars will consider the five available specimens: the holotype YPFB Pal 6251, which includes both maxillae and mandibles of a subadult individual (i.e. upper M4 are missing and m4 are unerupted); MHNC 13906 (which preserves complete maxillae and mandibles and 13931 a partial maxilla with M1-3). M1 is relatively different from the other molars and will be treated first. M2-M3, which have a more typical morphology as compared to most of the other Tiupampan metatherians will be described jointly. M4, which strongly differs from the preceding molar, as in most metatherians, will be studied next. M1 is a distinctive tooth of Incadelphys in the distolabial extension of its metastylar angle. As a consequence, the labial edge of M1 is much longer than on the other molars (Table 1). The anterior edge is shorter than on the posterior molars, and the tooth is longer than wide (1.56 mm vs 1.54mm; mean of five measurements, seeTable 1), a condition that contrasts with that of Andinodelphys, Pucadelphys, and Mizquedelphys. A condition of the M1 similar to that of Incadelphys is observed in the Campanian genus Aenigmadelphys of Utah. Table 3 compares the angle between the line joining stylar cusps D and E and the postmetacrista. Because the postmetacrista is often curved, and because the posterolabial part of the crista is relatively straight, the latter has been used for the measurement. As observed inTable 2, the mean of the angle obtained for pucadelphyids (53.2°) is approximately 48% and 32% greater than the angle of Incadelphys and Aenigmadelphys respectively. Because of this difficulty of measurement, the value of the angle obtained is certainly somewhat imprecise. However, because of the great difference observed, this result is probably significant. As a consequence of the posterolabial extension of the M1, its mesial edge is distinctly shorter than its labial edge. A similar condition is also observed in Aenigmadelphys. Marmosopsis from the early Eocene of Itaboraí, clearly ranges close to Incadelphys, whereas Monodelphis and Thylamys are closer to pucadelphyids than to Incadelphys and Aenigmadelphys. The protocone of M1 is relatively massive, being mesiodistally longer than wide on the three specimens. It is roughly symmetrical mesiodistally and does not present the distolingual inflation observed in didelphids and pucadelphyids. The mesial and distal bases of the protocone are smooth and bear no cingulum. Para- and metaconules are well-developed (almost as large as stylar cusps B and D). From the paraconule, a conspicuous paracingulum (i.e. labial extension of the preparaconular crista) extends up to stylar cusp A. Distally, the metaconule abuts the distal base of metacone but no metacingulum (i.e. labial extension of the postmetaconular crista) is present. The paracone is slightly smaller in height and volume than the metacone. Both cusps are widely separated at base, as in didelphids and pucadelphyids. A deep trigon basin is bordered by the distolingual aspect of the paracone, the mesiolingual aspect of the metacone and the labial aspect of the protocone. The lingual aspect of the para- and metacone is strongly convex, whereas their labial aspect is flat to slightly concave. As a consequence, the cusps are triangular in section and the pre- and post- paracristae and pre- and post-metacristae are shifted labially, forming the lingual wall of the stylar shelf. The junction of the postparacrista and premetacrista (i.e. the median point of the centrocrista) is displaced labially, and the centrocrista is slightly V-shaped in occlusal view. This condition, which is present in Aenigmadelphys, didelphids, and pucadelphyids, differs from that observed, for instance, in Kokopellia, alphadontids, peradectids, and sparassodonts, in which the labial and lingual aspects of the para- and metacone are markedly convex (generally slightly less convex labially than lingually), the pre- and post- paracristae and pre-and post-metacristae are in a median position relative to the para- and metacone and therefore the centrocrista is straight. The stylar shelf of Incadelphys is narrow, being almost absent anteriorly since the stylar cusp B is almost connate to the paracone to which it is connected by a very short preparacrista. The stylar cusp A is smaller than B but conspicuous. It surrounds posterolabially and imbricates with the posterobasal cusp of P3. Stylar cusp B and D are large and subequal in size, but variation exists. In MHNC 13906, StB is slightly smaller than StD, whereas in MHNC 13931 StB is slightly larger than StD; these cusps are subequal in the holotype. Stylar cusp B is conical, whereas stylar cusp D is transversely compressed. Between StB and StD, a small stylar cusp C is present in the holotype and MHNC 13906. Stylar cusp C is lacking in MHNC 13931. Stylar cusp E is indistinguishable. The labial edge of M1 is straight and features no ectoflexus. M2 and M3 are conspicuously wider than long. They differ from M 1 in the protocone, which is approximately as long as wide on M2 and clearly wider than long on M3. The stylar shelf is wider than on M1, especially its anterior part. As a consequence, the stylar cusp B is well separated from the paracone, and the preparacrista is as long as the postparacrista on M2 and slightly longer on M3. The preparacrista contacts stylar cusp B on its anterior edge, almost between cusp B and A on MHNC 13906. Stylar cusp C is small to absent and stylar cusp D is well developed but smaller than B. On the labial edge of M2 is a small ectoflexus (rather a notch) between stylar cusps B and C. On M3, the ectoflexus is deeper and located between stylar cusps C and D. From M1 to M3, at the distolabial corner of the tooth, the angle between the labial edge and the postmetacrista increases and, as a consequence, the postmetacrista is more transverse posteriorly. M2-M3 of Incadelphys strongly resemble those of Aenigmadelphys, from which they differ however in the latter being transversely wider and mesiodistally shorter (see comparison below p. 000). Furthermore, the M2-M3 of Aenigmadelphys have a slightly wider stylar shelf. On M4, the protocone is shorter mesiodistally than on the anterior molars and the metacone is greatly reduced compared to that of the anterior molars, being significantly smaller than the paracone. The anterior stylar shelf is wider and the preparacrista is longer than on M2-M3. The posterior stylar shelf is very narrow but still present labial to the metacone. The M4 of Incadelphys differs from that of Aenigmadelphys in the latter being mesiodistally shorter, transversely wider with a longer preparacrista, and in the posterior stylar shelf being virtually absent. Lower dentition Lower incisors (Figs 6; 7). The four incisors are preserved on the left dentary, but i1 is missing part of its crown. In the description below, we follow the interpretation of Hershkovitz (1982, 1995), that the four lower incisors of metatherians are serially homologous to i2-i5. On the right dentary i2-i4 are preserved but i5 is missing its crown. In size, the crown of i2 is smaller than that of i3 but larger than i4; i5 is the smallest of the four incisors. The crowns are peg-like but slightly spatulate, being wider than high. The apex of the crown of i2 is roughly semicircular in labial or lingual view; that of i3 is lanceolate with a carina on its lingual aspect; that of i4 is similar to i1 but smaller and that of i5 is also somewhat lanceolate. The i3 is distinctly staggered as indicated by the buttress visible on the anterolabial edge of the dentary just ventral to the labial aspect of the tooth and by the posterior shift of its root observable lingually on MHNC 13906. Lower canine (Figs 6; 7). The lower canine is a large tooth, although consistently smaller than the upper canine. It is pointed at its apex and curved (from the alveolar border) dorsally but not posteriorly. In other words, the apex of the tooth does not overhang the

Genus Incadelphys Marshall & Muizon, 1988 DIAGNOSIS. — Because the genus is monospecific, its diagnosis is that of the type species. TYPE SPECIES. — Incadelphys antiquus Marshall & Muizon, 1988 by original designation.

Genus Incadelphys Marshall & Muizon, 1988 DIAGNOSIS. — Because the genus is monospecific, its diagnosis is that of the type species. TYPE SPECIES. — Incadelphys antiquus Marshall & Muizon, 1988 by original designation., Published as part of Muizon, Christian de & Ladevèze, Sandrine, 2022, New material of Incadelphys antiquus (Pucadelphyda, Metatheria, Mammalia) from the early Palaeocene of Bolivia reveals phylogenetic affinities with enigmatic North and South American metatherians, pp. 609-643 in Geodiversitas 44 (22) on page 612, DOI: 10.5252/geodiversitas2022v44a22, http://zenodo.org/record/6795405, {"references":["MARSHALL L. G. & MUIZON C. DE 1988. - The dawn of the age of mammals in South America. National Geographic Research 4 (1): 23 - 55."]}

Simoclaenus sylvaticus Muizon & Cifelli, 2000 EMENDED DIAGNOSIS. ��� Dental formula: I?/?, C 1/1, P 4/4, M 3/3; relatively large short-snouted kollpaniine characterized by the strong mesiodistal compression of its lower molars and premolars, which is correlatively observed on the M2; upper canine transversely compressed; P1 vertically implanted; P2 with a small protoconal bulge on lingual side of paracone; P3-4 with well-developed protocone (slightly larger on P4); M1 much smaller than M2; M2 almost square in occlusal outline but distinctly asymmetrical as in Molinodus; p4 with a well-developed metaconid medial to protoconid; molars with a large metaconid, posterior to the protoconid and with a posterior projection that partially fills the talonid basin; protoconid distinctly smaller than in Andinodus; posterior wall of trigonid sigmoid in occlusal view; paraconid and paracristid smaller than in Andinodus; large hypoconid with a labial slope less vertical than in Andinodus; cristid obliqua meets trigonid on lingual edge of protoconid. Ascending process of the maxilla short, high, and erected, premaxilla-maxilla suture subvertical in lateral view; frontal-maxilla suture present (therefore absence of nasal-lacrimal suture) anterior opening of infraorbital canal at level of P3. Rostrum, blunt and short as indicated by cheek teeth mesiodistal compression, implantation of anterior premolars, and subvertical premaxilla-maxilla suture. HYPODIGM. ��� The type specimen, MHNC 8332, a fairly complete right dentary with the alveoli of c, p1, the roots of p2, the alveolus of p3, and p4-m3. The dentary is lacking the anterior region with the incisor alveoli and most of the coronoid process; MHNC 8348, a right maxilla with M1 lacking the parastylar region and part of the paracone and M2-3 complete; MHNC 13868, a right maxilla with root of the canine and P1-P4; MNHC 13872, a partial mandible with alveolus of p1, roots of p2-3and p4-m1; MHNC 13876 a right maxilla fragment with M1-M2. DESCRIPTION Three new specimens are referred to this species. MHNC 13872 is a mandible fragment with the alveolus of p1, the roots of p2-3 and p4-m1 (Fig. 7). The alveolus of p1 is vertical as in the holotype of Simoclaenus sylvaticus (MHNC 8332) (Muizon & Cifelli 2000), indicating that the tooth was not procumbent in contrast to the condition observed in Molinodus (see above). This feature, shared by the holotype of Simoclaenus sylvaticus and the new specimen clearly supports the referral of the latter rather than to Molinodus suarezi, the p1 of which is procumbent (Fig. 1A, B). However, the major characteristic of this specimen lies in its p4, which is markedly compressed mesiodistally as is observed on the holotype. As in the latter, the metaconid is placed lingually to the protoconid and is not shifted posteriorly as is observed in Molinodus suarezi (Fig. 1D). Furthermore, the p4 of MHNC 13872 has the same strongly bulbous morphology as that of the holotype. The m1 is relatively worn but does not depart significantly from that of the holotype in terms of morphology. However, the two specimens differ in their size and the new specimen described here is distinctly smaller than the holotype (Table 2). As a matter of fact, the p4 and m1 of the new specimen are in average 10% smaller than those of the holotype (mean of the four ratios of Table 2). Although significant, this difference could be interpreted as related to individual size variation. The other large ���condylarth��� to which this specimen could be related is Molinodus suarezi, although this taxon is clearly smaller than Simoclaenus sylvaticus. However, the p4 observed on the mandible of M. suarezi described above (Fig. 2A) is so different from that of MHNC 13872 that we rather favor a strong individual size variation in S. sylvaticus than morphological variation in M. suarezi. A well-preserved lateral ascending process of a right maxilla (MHNC 13868) is referred to Simoclaenus sylvaticus. This specimen bears the root of the canine and the four premolars, which were unknown for this taxon (Fig. 8). The upper premolars of MHNC 13868 are only slightly larger than those of Molinodus suarezi described by Muizon & Cifelli (2000: 59), but this difference could be interpreted as related to individual variation in size. The major criterion that convinced us to relate this specimen to S. sylvaticus is the size of the canine. Although the crown of that tooth is not preserved the section of the root at the level of the alveolar border is relevant to its size. It is noteworthy that no upper canine is known for M. suarezi. We therefore compared the section of the upper canine of MHNC 13868 to that of the lower canine of MHNC 13883. Because the Tiupampa kollpaniines are relatively unspecialized, it is hypothesized that the width and length (at the level of the alveolar plane) of the upper and lower canines did not differ significantly even if generally the upper canines are slightly larger than the lowers. This remains an assumption, as no kollpaniine has ever been documented by both upper and lower canines. Here, the upper canine of MHNC 13868 (Simoclaenus) is 87% longer and 55% wider than the lower canine of MHNC 13883 (Molinodus) (Table 3). Even taking into account the approximation in comparing upper and lower canines, such a size difference is highly significant and we regard as unlikely that the two canines could belong to the same taxon of kollpaniine. We therefore, tentatively refer MHNC 13868 to S. sylvaticus rather than to M. suarezi. Furthermore, the size difference between the P4 and M1 of the holotype of S. sylvaticus and referred specimen described here could be related to sexual dimorphism in this species as evoked above. The premolars are well preserved and bear very reduced dental wear. The size of P3 and P4 is slightly larger than the equivalent teeth in Molinodus suarezi, which are known on one specimen only (MHNC 1247) (see Muizon & Cifelli 2000: 58) (Table 4). P1 and P2 are unknown for M. suarezi. Although this size difference is moderate (c. 10%), because of the large size of the canine, we rather refer this specimen to Simoclaenus sylvaticus. Furthermore, the anteroposterior length of the upper premolar row of MHNC 13868 (11.31 mm) is only slightly smaller than the lower premolar row of the holotype of S. sylvaticus (11.97 mm), on which the alveoli of p1-3 and the p4 are preserved. Therefore, the mesiodistal length of the upper premolar row of the new specimen (MHNC 13868) correctly matches the length of the lower premolars row of the holotype (MHNC 8348). P1 is peg-like, single-rooted, and compressed transversely. It is implanted vertically in the maxilla as is observed on the alveolus of the p1 of the holotype (MHNC 8348). This condition suggests a relative shortness of the rostrum and is congruent with the anteroposterior compression of the lower cheek teeth observed on the mandible. It is noteworthy that the p1 of Molinodus described above (MHNC 13883) differs from the condition observed in Simoclaenus in being slightly procumbent, thus suggesting a more elongated rostrum. As preserved, the P1 of Simoclaenus on MHNC 13868 is longer than high and no significant wear facet can be observed at the apex of its crown. In lateral view the tooth is roughly symmetrical anteroposteriorly. A small diastema separates P1 from the canine anteriorly and from P2 posteriorly. P2 is triangular in occlusal view and bears three roots. It is longer than wide. It presents a conspicuous inflation on its distolingual edge, which can be regarded as an incipiently developed protocone (protoconal bulge). The paracone forms most of the tooth and is as high as long. Its mesial edge is wide and blunt whereas its distal edge is thin and forms a sharp crest. The tooth bears no cingulum but a small cusp at the distolabial edge of the paracone could be regarded as a metastyle. This style contacts the anterior edge of P3 and no diastema separates the two teeth. P3 is slightly wider than long, triangular in occlusal view, and bears three roots. The mesial and distal edges are markedly concave, a condition which individualizes a well-developed protocone lingually. This cusp is approximately two thirds the height of the paracone. It is as long as wide. It has a very convex lingual edge and a flat labial aspect. These two edges of the tooth are separated by sharp pre- and postprotocristae, which join the base of the crown at the level of the greatest concavity of the mesial and distal edges of the tooth. Labially the paracone is approximately twice as long as wide. Its mesial edge bears a smooth crest and its distal crest is slightly obliterated by an elongated wear facet, which extends from the apex of the tooth to the posterior base of the paracone. At the mesial angle of the paracone is a marked parastyle. From this cusp, a conspicuous cingulum extends on labial edge of the paracone. At the distal end of the cingulum is a small metastyle. P4 has a pattern similar to that of P3 but it is mesiodistally shorter and transversely wider. Its mesial and distal edges are slightly concave but to a much lesser extent than the condition observed on P3. The paracone is smaller (in height and volume) and the protocone is more voluminous than on the preceding tooth. The pre- and postprotocristae are more developed than on P3 and extend on the anterior and posterior edges of the paracone. The postprotocrista even joins the distolabial angle of the tooth and contacts the postparacrista. The latter bears a narrow wear facet on its mesial two thirds only. The distal end of the postparacrista bears, on its lingual aspect, a hint of inflation, which can be interpreted as an incipient metacone. A tiny inflation on the postprotocrista may also be regarded as an incipient metaconule. On the distal edge of the protocone, is a distinct postcingulum. On its mesial edge the precingulum is weakly developed. On the mesiolabial angle of the tooth the parastyle is more developed than on P3. From this style, a well-developed labial cingulum extends distally until the metastylar angle of P4. Little is preserved of the palatal process of the maxilla, but the lateral wall of the rostrum from the anterior edge of the canine to the anterior root of the zygomatic arch is relatively complete and all its edges likely correspond to sutures with adjacent bones except for a small U-shaped-break in the posterodorsal angle (Fig. 8C). The anterodorsal edge of the specimen probably corresponds to the nasal-maxilla suture. Approximately above the P1-P2 embrasure, the edge of the maxilla distinctly protrudes medially. Anterior to this indentation, the suture is apparently anteroposteriorly oriented or slightly oriented anterolaterally. Posterior to it, the suture diverges posterolaterally, thus indicating a widening of the nasals posteriorly, as generally observed in early diverging metatherians and eutherians (e.g., deltatheroidans, pucadelphydans, Zalambdalestes, Kulbeckia, Alcidedorbignya). On the posterior limit of the maxilla, as preserved, is a deep groove probably for the articulation of the anterior process of the jugal. This groove (maxillajugal suture) approximately corresponds to the level of the anterior edge of the orbit and the posterior limit of the rostrum, which corresponds to the posterior edge of P4. On the posterodorsal angle of the specimen, in lateral view, is a distinct small notch (dorsal to the breakage notch mentioned above), which was receiving the anterolateral angle of the frontal. If this interpretation is correct, the nasal and lacrimal of Simoclaenus were distinctly separated, which likely represents a crown Placentalia condition (frontal-maxilla suture present) (Muizon et al. 2015). The posterior edge of the maxilla, between this notch and the dorsal end of the jugal groove, likely corresponds to the lacrimal-maxilla suture. Anteriorly, several grooves mark the edge of the maxilla immediately anterior to the canine, which we interpret as the premaxilla-maxilla suture. This suture is almost straight, slightly concave anteriorly, and sub-vertical, forming an angle of approximately 95�� with the alveolar plane (Fig. 8C). The lateral aspect of the maxilla is markedly elevated and erected, to a greater extent than the condition observed in the pantodont Alcidedorbignya inopinata from the same locality (Muizon et al. 2015). This condition apparently resembles that of Baioconodon nordicum (YPM-PU 14234) from the earliest Palaeocene (Puercan) of Mantua lentil of Wyoming. The anterior opening of the infraorbital canal is 2.08 mm high and located above the mesiolabial root of P3. In this respect Simoclaenus differs from the condition in Maiorana and Baioconodon, in which the infraorbital foramen is located more posteriorly, above the mesiolabial root of P4. A condition similar to that of Maiorana and Baioconodon is observed in Didolodus multicuspis (MACN 10690), in which the infraorbital foramen is located above the distal edge of P3 and most of the P4 (Gelfo, personal communication). Anterior to this foramen is a tiny opening located above the anterior root of P2, and which probably represents a nutrient foramen. In its anterior region, the maxilla is not inflated laterally by the canine as is observed in Alcidedorbignya, due to the fact that the canine was compressed transversely. This condition particularly resembles the ���condylarths��� of Mantua lentil of Wyoming, Baioconodon and Maiorana. The third specimen referred to Simoclaenus sylvaticus is a partial maxilla with M1-2 (MHNC 13876), (Fig. 9). The M2 perfectly matches the size and morphology of that of MHNC 8348 described by Muizon & Cifelli (2000). The small differences between the two teeth are the presence, in MHNC 13876, of a slightly larger parastyle, a cuspule on the preparaconular crista located between the paraconule and the parastyle and a slight inflation of the lingual end of the precingulum (cuspule?). The M2 of MHNC 13876 has the characteristic asymmetrical morphology observed in Molinodus and Simoclaenus, in which the paracone is distinctly more labial than the metacone (Muizon & Cifelli 2000: fig. 2A-C, fig. 14C). This condition is not observed on the M1 of Molinodus, the paracone of which is not shifted labially. The most interesting characteristic of this specimen is in the relative wear stage of the M2 and M1. The M2 has a wear stage approximately similar to that of the M2 of MHNC 8348. In contrast the M1 is totally excavated in its lingual two thirds: the protocone, the protocristae and the conules, the pre-and postcingula, and the trigon basin have disappeared; the only preserved elements of the tooth are the para- and metacones, the styles and the labial cingulum. This wear stage is clearly more advanced than that observed on the M1 of MHNC 8348, in which the protocone and conules are coalescent but still identifiable, the protocristae and the pre-and postcingula are distinctly observable. This stage of wear of M2-1 of MHNC 8348 is comparable to that observed on the maxilla of Molinodus suarezi (MHNC 1247) described by Muizon & Cifelli (2000). In fact, the extensive wear of the M1 of MHNC 13876 is comparable to the condition that could be observed on a DP4, an interpretation impossible given the fact that the posterior tooth is undoubtedly an M2, which presents the characteristic asymmetrical morphology of that tooth (Muizon & Cifelli 2000). Furthermore, the roots of the M1 are long and the lingual root perforates the floor of the orbit, which suggests that it is not a deciduous molar. In ventral view, laterally to M2, the maxillar process of the zygoma and the anterior border of the orbitotemporal fossa are preserved. The latter is at the level of the apex of the metacone of M2, while it is at the level of the paracone of M3 on the maxilla (MHNC 8348) referred to Simoclaenus by Muizon & Cifelli (2000). In Molinodus the anterior edge of the orbitotemporal fossa is at the level of the paracone of M3 and in Baioconodon (YPM-PU 14234) and Maiorana (YPM-PU 16667 and 14171) it is at the level of the metacone of M3. However, this condition is likely to be individually variable since in Alcidedorbignya inopinata out of 13 specimens, in which it can be observed, three of them (see Muizon et al. 2015: fig. 10B) have an anterior edge of the orbitotemporal fossa at the level of the metacone of M2, as observed in the Simoclaenus specimen described here. In the other ten specimens, the anterior edge of the fossa is at the level of the paracone of M3. In the Alcidedorbignya sample the anterior position of M2 is observed in young adults and may be related to the ontogenetic increase of the length of the rostrum., Published as part of Muizon, Christian de, Billet, Guillaume & Ladev��ze, Sandrine, 2019, New remains of kollpaniine " condylarths " (Panameriungulata) from the early Palaeocene of Bolivia shed light on hypocone origins and molar proportions among ungulate-like placentals, pp. 841-874 in Geodiversitas 41 (25) on pages 851-855, DOI: 10.5252/geodiversitas2019v41a25, http://zenodo.org/record/3699898, {"references":["MUIZON C. DE & CIFELLI R. L. 2000. - The \" condylarths \" (archaic Ungulata, Mammalia) from the early Palaeocene of Tiupampa (Bolivia): implications on the origin of the South American ungulates. Geodiversitas 22 (1): 47 - 150.","MUIZON C. DE, BILLET G., ARGOT C., LADEVEZE S. & GOUSSARD F. 2015. - Alcidedorbignya inopinata, a basal pantodont (Eutheria, Mammalia) from the early Palaeocene of Bolivia: anatomy, phylogeny, and palaeobiology. Geodiversitas 37 (4): 397 - 634. https: // doi. org / 10.5252 / g 2015 n 4 a 1"]}

Tiuclaenus minutus Muizon & Marshall, 1987 DIAGNOSIS. ��� See Muizon & Cifelli (2000). DESCRIPTION A maxilla with M1-3 (MHNC 13879) is referred to Tiuclaenus minutus. It bears three almost unworn molars, and has been referred to this species essentially on the basis of its size (Fig. 10A). Tiuclaenus minutus is the smallest ���condylarth��� species of the Tiupampa fauna and the molars of the new specimen are even slightly smaller than those of MHNC 1240 described by Muizon & Cifelli (2000: fig. 7C). For example, the length of the molar row is 5.86 mm in MHNC 13879, while it is 6.74 mm on MHNC 1240, but such a size difference is likely related to individual variation. The size and proportions of the upper molar of this specimen depart from the other species of Tiuclaenus and from Pucanodus, which are distinctly larger (see Muizon & Cifelli 2000: tables 7-9). However, some slight morphological differences exist between the specimens referred to T. minutus, which differ in the larger size of the para- and metastyles, the para-and metacones more approximated, the more pronounced ectoflexus and labial cingulum. Nevertheless, in spite of these morphological differences we tentatively refer MHNC 13879 to T. minutus, considering that they could regarded as related to individual variation, an interpretation that could be revised when a larger sample of that species will be available., Published as part of Muizon, Christian de, Billet, Guillaume & Ladev��ze, Sandrine, 2019, New remains of kollpaniine " condylarths " (Panameriungulata) from the early Palaeocene of Bolivia shed light on hypocone origins and molar proportions among ungulate-like placentals, pp. 841-874 in Geodiversitas 41 (25) on page 856, DOI: 10.5252/geodiversitas2019v41a25, http://zenodo.org/record/3699898, {"references":["MUIZON C. DE & MARSHALL L. G. 1987 - Le plus ancien Condylarthre (Mammalia) sud-americain (Cretace superieur, Bolivie). Compte Rendus hebdomadaires des Seances de l'Academie des Sciences 304: 771 - 774.","MUIZON C. DE & CIFELLI R. L. 2000. - The \" condylarths \" (archaic Ungulata, Mammalia) from the early Palaeocene of Tiupampa (Bolivia): implications on the origin of the South American ungulates. Geodiversitas 22 (1): 47 - 150."]}

Pucanodus gagnieri Muizon & Marshall, 1991 DIAGNOSIS. ��� See Muizon & Cifelli (2000). DESCRIPTION A mandible fragment bearing m2-3 (MHNC 13869) has been referred to Pucanodus gagnieri (Fig. 11) because it presents the mesiodistal compression of the molars especially m3, which is characteristic of that species (Muizon & Marshall 1991). The specimen is approximately of the size of a small Tiuclaenus. The teeth are almost unworn and better illustrate this taxon than the holotype (a mandible with p3-m3), the teeth of which, are notably worn. The massive proportions of the teeth (large width relative to length) and particularly the shortness of the talonid of m3 are conspicuous on this specimen. As in all kollpaniines and North American mioclaenines, the entoconid and hypoconulid are connate (almost confluent) and the talonid basin is an obliquely oriented groove open anterolingually. Measurements are provided on Table 5., Published as part of Muizon, Christian de, Billet, Guillaume & Ladev��ze, Sandrine, 2019, New remains of kollpaniine " condylarths " (Panameriungulata) from the early Palaeocene of Bolivia shed light on hypocone origins and molar proportions among ungulate-like placentals, pp. 841-874 in Geodiversitas 41 (25) on page 856, DOI: 10.5252/geodiversitas2019v41a25, http://zenodo.org/record/3699898, {"references":["MUIZON C. DE & MARSHALL L. G. 1991. - Nouveaux Condylarthres du Paleocene inferieur de Tiupampa (Bolivie). Bulletin du Museum national d'Histoire naturelle, section C, Sciences de la Terre, 4 eme serie, 13: 201 - 225. https: // biodiversitylibrary. org / page / 55803145","MUIZON C. DE & CIFELLI R. L. 2000. - The \" condylarths \" (archaic Ungulata, Mammalia) from the early Palaeocene of Tiupampa (Bolivia): implications on the origin of the South American ungulates. Geodiversitas 22 (1): 47 - 150."]}

Molinodus suarezi Muizon & Marshall, 1987 EMENDED DIAGNOSIS. ��� Size similar to that of Promioclaenus; dental formula I?/3, C?/1, P?/4, M3/3; P3 triangular, with a strong parastyle anterior to paracone; pre- and postparacristae well-developed; protocone is a well-developed cusp and distincly individualized from the paracone but slender with slight pre- and postcingula; P4 more massive, shorter, and wider than P3, with small conules; protocone only slightly larger than on P3 but more massive; wellmarked pre- and postcingula, and strong labial cingulum; M1 triangular and almost symmetrical in relation to its transverse axis; protocone transversely compressed with an oval-shaped apical wear facet; metacone only slightly lingual to the paracone; welldeveloped cingula (pre-, post- and labial); styles slightly to not projected labially; no hypocone; M2 subquadrangular and strongly asymmetrical, with oblique labial edge; well-developed pre- and postcingula, not reaching the para- and metastyles (but close to them); labial cingulum very strong; protocone large, bulbous, and mesiodistally elongated with incipient duplication; conules large; well-developed para- and metacingula reaching para- and metastyles; paracone higher and more voluminous than metacone; metacone much more lingual than paracone; centrocrista straight; para- and metastyles almost aligned with para- and metacones but parastyle still slightly shifted labially; no well-individualized hypocone; M3 much wider than long; strongly bent posteriorly; labial edge strongly oblique; little reduced (i.e. only slightly shorter than M2); metacone and metaconule reduced; i1 and i2 distinctly larger than i3; i2 staggered; lower canine short and robust; p1 single-cusped, single-rooted, and procumbent; p2 triangular in lateral view; transversely flattened; small posterior cusp; p4, much larger; variable in shape from triangular to quadrate, with a large metaconid appressed against protoconid; anterior crest of protoconid possessing a tiny paraconid; large talonid cusp; lower molars with bulbous cusps; trigonid and talonid basin reduced; strong pre- and small postcingulids (on m1 and m3 only); paraconid clearly smaller than and appressed against metaconid; paracristid transverse and arched distally; metaconid distolingual to and slightly smaller than protoconid; cristid obliqua variable in size and reaching labial edge of metaconid; talonid basin small and open lingually (more an oblique groove than a basin); hypoconid large, inflated, circular, and only slightly smaller than protoconid; entoconid and hypoconulid almost completely fused forming a distolingual oblique crest; talonid of m3 larger than on m1-2 with hypoconulid as large as hypoconid. On the dentary presence of a well-developed coronoid crest separated from the labial edge of m3 by a coronoid fossa. Among Tiupampa ���condylarths���, Molinodus more resembles Simoclaenus than the other taxa. However, Molinodus differs from Simoclaenus in its smaller size, its cheek teeth more elongated mesiodistally, its upper molar less transverse, its M2 more asymmetrical with an mesiolabially projected parastyle, its procumbent p1, and its longer rostrum. Molinodus differs from Promioclaenus in its molars, which are more bulbous with apices of the cusps more approximated, in the longer trigonid of the lower molars with a paraconid less appressed against the metaconid, in the presence of a generally distinct labial cingulum, in the non-reduced m3, in the more transverse and less bulbous upper molars, in the thinner postcingulum, in the strong asymmetry of the M2 with an mesiolabially projecting parastyle, and in the unreduced M3. HYPODIGM. ��� As in Muizon & Cifelli (2000) with the additional following specimens: MHNC 13883, a partial left mandible with alveoli of incisors, canine, p1, roots of p2, alveoli of p3 and alveolus of anterior root of p4; MHNC 13867, a partial left mandible with p3-m3; MHNC 13870, a partial left maxilla with M1-M3, with M1 and M2 missing the labial edges of para- and metacones. DESCRIPTION An anterior fragment of left mandible of Molinodus suarezi (Fig. 1) bears the labial edge of the alveoli of the three incisors, the canine, the p1, the roots of p2, the alveoli of p3, and the anterior alveolus of p4 (MHNC 13883). On the medial aspect of the dentary a large symphyseal surface for the intermandibular suture is present. This surface is in one plane with sharp edges, but it is rough and bears numerous ridges and grooves probably interlocking with the symmetrical surface on the other mandible. The two symphyseal surfaces were therefore tightly attached one to the other, but the symphysis was clearly unfused on this specimen. Although ligamentous, it is likely that the symphysis was quite rigid and allowed little intermandibular movements. Because the roots of p3 extends as far as the ventral region of the dentary leaving no space of a potential unerupted tooth germ, we regard that the definitive p3 was erupted. Because the preserved teeth (c and i1) are absolutely unworn, this specimen is interpreted as belonging to a young adult. It is, therefore, not impossible that ontogenetically older individuals may have had a fused symphysis. On the labial side of the dentary a large anterior mental foramen is present ventral to the embrasure between p1 and p2. Although the incisors are missing, the anteriormost region of the dentary is preserved with the labial edge of the incisors alveoli. The dentary is broken vertically in this region and the lingual portion of the alveoli is missing; therefore, a vertical section of the incisors alveoli can be observed. Based on the size of the roots, i1 was apparently the largest of the three incisors or was, at best, similar in size to i2. The i3 is clearly the smallest of the three incisors. Interestingly, the alveolus of i2 presents a distinct lingual shift of its root. As a consequence, the vertical section the alveolus is clearly triangular whereas that of the other alveoli are cylindrical with parallel edges (Fig. 1B, E). This condition of the i2 of Molinodus, is identical to the staggered second incisor, (the i3 according to Hershkovitz 1982, 1995), of many metatherians (e.g., stagodontids, pucadelphyids, sparassodonts, didelphids, microbiotheres, peramelids, thylacinids, dasyurids). The triangular section of the alveolus of the staggered incisor is clearly observed on the figure 5 of Hershkovitz (1982). It is not the first time that a staggered second incisor is described in a eutherian since Hershkovitz (1982: 197) mentions this condition in several extant Carnivora. Among the Tiupampa eutherians, it is absent in Alcidedorbignya inopinata (Muizon et al. 2015), and there is no indication that it was present in Tiuclaenus minutus and Pucanodus gagneri, the only other Tiupampa eutherians that preserve the anterior portion of the dentary. It may be the first time that this trait is observed in a fossil eutherian, but this is probably due to the fact that the anterior portion of the dentary is rarely preserved in fossil mammals. In dorsal view, the three lower incisors are set in a slightly oblique row, relative to the symphyseal plane (Fig. 1C). In other words, i1 is anteromedial to i2, and i3 is posterolateral to i2. The lower incisor tooth row was, therefore, more or less parabolic or V-shaped. The last incisor, i3, was closely appressed against the mesial edge of the canine as indicated by the posi- tion of the i3 alveolus. The canine is a moderately developed tooth but it is robust. The height of the crown (4.60 mm) is approximately twice its mesio-distal length (2.44 mm) at base. The canine is transversely compressed, being distinctly narrower (1.75 mm) at its base than long (2.44 mm). The posterior curvature of the canine is weak and its posterior edge is only very slightly concave. Its mesial edge is distinctly convex. On the mesiolingual edge of the tooth a blunt ridge extends mesioventrally on the dorsal half of the crown and distoventrally on the ventral half (Fig. 1B). In dorsal view, the labial side of the canine is strongly convex, whereas it is almost flat to slightly concave on its lingual side. In labial view the main axis of the crown is moderately oblique in relation to the alveolar plane, with which it forms an angle of approximately 110��. Posterior to the canine is a small p1 separated from the former by a small but distinct diastema. The p1 is single-rooted. It is slightly procumbent and asymmetrical in labial view. The crown of the tooth is markedly compressed transversely. It bears a pronounced mesial crest, which is slightly convex. The distal edge of the tooth is straight and bears a small cuspule at its base (Fig. 1D). There is no cingulum at the base of the crown. The lingual aspect of the crown in markedly concave and its labial edge is convex. As a consequence, in distal view the crown is slightly bent lingually. The roots of p2 are preserved in the dentary of MHNC 13883. The very short diastema, which separates p2 from p1, is approximately twice shorter than the diastema anterior to p1. A similar condition is observed on MHNC 1243, a mandible fragment, which preserves the root of c, the alveolus of p1 and p2 (see Muizon & Cifelli 2000). Interestingly, on MHNC 13883 the roots of p2 are set obliquely in the dentary and the anterior root is mesiolabial to the posterior one. The mesiodistal axis of the tooth is approximately at an angle of 30�� with the anteroposterior axis of the tooth row (from c to p4) (Fig. 1D). Because this condition is not present in MHNC 1243, it could represent a pathological condition or an individual variation in MHNC 13883. Posterior to p2, the alveoli of p3 indicate that the tooth was implanted parallel to the axis of the tooth row. The p2 and p3 were not separated by a diastema and were closely appressed one against the other. A relatively complete left mandible of Molinodus suarezi (MHNC 13867) bears p3-4 and m1-3 (Fig. 2). The most interesting element of this specimen lies in its premolars. The teeth are relatively narrow transversely being c. 30% longer than wide. They are roughly triangular in lateral view and are approximately as high as long. The p3 is slightly more slender than the p4 but both teeth are built on a similar pattern. The mesial edge of p3 bears a sharp crest with a marked angulation on the dorsal third of the crown. The largest cusp of the tooth, the protoconid, is transversely narrow and its lingual edge is slightly concave lingually, in its dorsal region. More ventrally it is inflated and convex. The distolingual angle of the protoconid bears a strong inflation, which reaches the dorsal half of the distal edge of the tooth in lingual view. This structure corresponds to the development of a small metaconid. At the mesial base of the tooth is a small cingulum, which is continuous from the distolabial to distolingual edges of the mesial root. Distally a well-developed talonid cusp forms the base of the crown and extends transversely in a robust and rounded cingulum from the distolabial to the distolingual angle of the tooth. In occlusal view, p3 is distinctly wider distally than mesially. The p4 is slightly longer than the p3. Its mesial edge bears a sharp crest that shifts lingually at mid-height of the crown. There, it forms a small tubercle interpreted as an incipient paraconid. The protoconid is strongly convex labially and flat lingually. On its distolingual edge is a large metaconid. In dorsal view, it is slightly smaller than the protoconid and its apex is distinctly distal to that of the protoconid. On the mesial edge of the protoconid, a sharp and well-developed paracristid connects to the paraconid mesially. Posterior to the trigonid, the talonid does not bear differentiated cusps but forms a thick distobasal ridge, which extends from the mesiolingual to mesiolabial aspects of the distal root. The distal edge of the tooth is slightly wider than the mesial one. The condition of the p4 of MHNC 13867 distinctly departs from the morphology of the isolated p4 (MHNC 1244) referred to Molinodus suarezi by Muizon & Cifelli (2000: fig. 3M, N). On MHNC 1244 the metaconid is almost totally lingual to the protoconid and not shifted distally. Furthermore, the crown of the tooth is markedly more massive, strongly compressed mesiodistally, and more inflated transversely. As a whole, MHNC 1244 more resembles the p4 of Simoclaenus sylvaticus in all its features but is clearly much smaller. When compared to the size of the roots observed on the holotype of S. sylvaticus, it is even too small to be a p3 of and it is also slightly too small to be a p2. In other respects, the large metaconid and the well-developed paraconid and paracristid of MHNC 1244 are more compatible with the morphology generally observed on a p4. Therefore, we think that MHNC 1244 is actually a p4 and that, either, the morphology of the p4 of M. suarezi is highly variable or MNHC 1244 represents a new taxon at Tiupampa. Given the size difference it is unlikely that it could be referred to S. sylvaticus, except if this species is sexually dimorphic, which is unknown yet. However, given the lack of a representative sample of M. suarezi and S. sylvaticus, this uncertainty cannot be resolved so far. The three molars have the characteristic features of Molinodus suarezi as described by Muizon & Cifelli (2000). The trigonid bears a well-developed paraconid but distinctly smaller than the metaconid and placed mesial to it or slightly labial (on m1). The paraconid is closely appressed against the metaconid. The latter is large, almost as large as the protoconid and located distolingual to it. As a consequence, the protocristid is obliquely oriented (mesiolabially-distolingually) as compared to the axis of the tooth row. On m1 and m2 the talonid is slightly narrower than the trigonid. The cristid obliqua extends from the large hypoconid to the central region of the protocristid. Lingually, the hypoconulid and the entoconid are connate and the talonid basin is in fact an obliquely oriented groove that opens mesiolingually as is observed in all kollpaniines. On m3 the hypoconulid is much larger than on the other molars and is as large as the hypoconid. The small size of the m1 relatively to the other molars is noteworthy. This feature is present in all kollpaniines but it is especially pronounced in the holotype (YPFB Pal 6112) of M. suarezi (Muizon & Cifelli 2000: fig. 3A) and MHNC 13867 (Table 1). On the dentary of MHNC 13867, the posteriormost mental foramen is located below the anterior root of p4. The corpus mandibularis of MHNC 13867 and 13871 is relatively massive especially in the latter. On both specimens, most of the ramus mandibularis is missing, except the anterior portion of the coronoid process. In the region of the retromolar space, the anterior basis of the coronoid process is very wide and bears a conspicuous labially opening coronoid fossa. The fossa is much deeper on MHNC 13871 than on 13867. Lateral to the fossa, the coronoid crest is salient and extends ventrally on the lateral aspect of the dentary (Fig.3). This condition indicates a powerful masseter muscle, which inserts in the masseteric fossa and on the coronoid crest and is congruent with the stoutness of the corpus mandibularis. A robust coronoid crest is observed on the other specimens of M. suarezi (YPFB Pal 6114, MHNC 8269) and on the large kollpaniines (Simoclaenus and Andinodus). It is absent or barely present in Tiuclaenus and Pucanodus, which are the smallest kollpaniine taxa (see Muizon & Cifelli 2000). A partial left maxilla referred to Molinodus suarezi (MHNC 13870) bears the three molars and is the first specimen discovered with an M3 associated to the anterior molars (Figs 4; 5; 6). The M3 referred by Muizon & Cifelli (2000: fig. 2, E) to M. suarezi is an isolated specimen and its referral had yet to be confirmed. M1 and M2 of MHNC 13870 are incomplete and are missing most of the labial edges of the para- and metacones and all the stylar regions and labial cingulum. M3 of MHNC 13870 is complete. M1 and M2 of MHNC 13870 preserve the lingual half of the tooth. The large protocone bears large conules which are similar to those already described in Molinodus. The mesial and distal edges of M1-2 present well-developed pre- and postcingulae, which extended labially until the stylar area of the teeth. The most interesting cusp of this specimen is the protocone. On M1-2 as is observed on the molars of M. suarezi described by Muizon & Cifelli (2000), the protocone is mesiodistally elongated and its wear facet is markedly ovale-shaped. On the M2 of MHNC 13870, the wear facet is constricted and the protocone bears vertical grooves, which reach the apex of the cusp. As a consequence, the latter is distinctly bilobate (Fig. 5). The posterior lobe of the protocone of MHNC 13870 receives the postprotocrista, which links it to the metaconule. This bilobate condition is even more pronounced than in MHNC 8280 (Muizon & Cifelli 2000: fig. 2A) as it concerns more than the apex of the cusp and extends dorsally on the protocone. It indicates that the duplication of the apical region of the protocone was almost certainly observable on the dentine at the enamel-dentine joint (see Anemone et al. 2012). The M3 of MHNC 13870 is remarkably similar to the isolated tooth referred to Molinodus suarezi by Muizon & Cifelli (2000) and does not require further description., Published as part of Muizon, Christian de, Billet, Guillaume & Ladev��ze, Sandrine, 2019, New remains of kollpaniine " condylarths " (Panameriungulata) from the early Palaeocene of Bolivia shed light on hypocone origins and molar proportions among ungulate-like placentals, pp. 841-874 in Geodiversitas 41 (25) on pages 844-851, DOI: 10.5252/geodiversitas2019v41a25, http://zenodo.org/record/3699898, {"references":["MUIZON C. DE & MARSHALL L. G. 1987 - Le plus ancien Condylarthre (Mammalia) sud-americain (Cretace superieur, Bolivie). Compte Rendus hebdomadaires des Seances de l'Academie des Sciences 304: 771 - 774.","MUIZON C. DE & CIFELLI R. L. 2000. - The \" condylarths \" (archaic Ungulata, Mammalia) from the early Palaeocene of Tiupampa (Bolivia): implications on the origin of the South American ungulates. Geodiversitas 22 (1): 47 - 150.","HERSHKOVITZ P. 1982. - The staggered marsupial lower third incisor (i 3). Geobios, memoire special, 6: 191 - 200. https: // doi. org / 10.1016 / S 0016 - 6995 (82) 80113 - 7","HERSHKOVITZ P. 1995. - The staggered marsupial lower incisor: hallmark of cohort Didelphimorphia. and description of a new genus and species with staggered i 3 from the Albian (Lower Cretaceous) of Texas. Bonner Zoologische Beitrage 45 (3 - 4): 153 - 169. https: // biodiversitylibrary. org / page / 44799597","MUIZON C. DE, BILLET G., ARGOT C., LADEVEZE S. & GOUSSARD F. 2015. - Alcidedorbignya inopinata, a basal pantodont (Eutheria, Mammalia) from the early Palaeocene of Bolivia: anatomy, phylogeny, and palaeobiology. Geodiversitas 37 (4): 397 - 634. https: // doi. org / 10.5252 / g 2015 n 4 a 1","ANEMONE R. L., SKINNER M. M. & DIRKS W. 2012. - Are there two distinct types of hypocone in Eocene primates? The ' pseudohypocone' of notharctines revisited. Palaeontologia electronica 15 (3): 26 A, 13 p."]}

Simoclaenus sylvaticus Muizon & Cifelli, 2000 EMENDED DIAGNOSIS. — Dental formula: I?/?, C 1/1, P 4/4, M 3/3; relatively large short-snouted kollpaniine characterized by the strong mesiodistal compression of its lower molars and premolars, which is correlatively observed on the M2; upper canine transversely compressed; P1 vertically implanted; P2 with a small protoconal bulge on lingual side of paracone; P3-4 with well-developed protocone (slightly larger on P4); M1 much smaller than M2; M2 almost square in occlusal outline but distinctly asymmetrical as in Molinodus; p4 with a well-developed metaconid medial to protoconid; molars with a large metaconid, posterior to the protoconid and with a posterior projection that partially fills the talonid basin; protoconid distinctly smaller than in Andinodus; posterior wall of trigonid sigmoid in occlusal view; paraconid and paracristid smaller than in Andinodus; large hypoconid with a labial slope less vertical than in Andinodus; cristid obliqua meets trigonid on lingual edge of protoconid. Ascending process of the maxilla short, high, and erected, premaxilla-maxilla suture subvertical in lateral view; frontal-maxilla suture present (therefore absence of nasal-lacrimal suture) anterior opening of infraorbital canal at level of P3. Rostrum, blunt and short as indicated by cheek teeth mesiodistal compression, implantation of anterior premolars, and subvertical premaxilla-maxilla suture. HYPODIGM. — The type specimen, MHNC 8332, a fairly complete right dentary with the alveoli of c, p1, the roots of p2, the alveolus of p3, and p4-m3. The dentary is lacking the anterior region with the incisor alveoli and most of the coronoid process; MHNC 8348, a right maxilla with M1 lacking the parastylar region and part of the paracone and M2-3 complete; MHNC 13868, a right maxilla with root of the canine and P1-P4; MNHC 13872, a partial mandible with alveolus of p1, roots of p2-3and p4-m1; MHNC 13876 a right maxilla fragment with M1-M2. DESCRIPTION Three new specimens are referred to this species. MHNC 13872 is a mandible fragment with the alveolus of p1, the roots of p2-3 and p4-m1 (Fig. 7). The alveolus of p1 is vertical as in the holotype of Simoclaenus sylvaticus (MHNC 8332) (Muizon & Cifelli 2000), indicating that the tooth was not procumbent in contrast to the condition observed in Molinodus (see above). This feature, shared by the holotype of Simoclaenus sylvaticus and the new specimen clearly supports the referral of the latter rather than to Molinodus suarezi, the p1 of which is procumbent (Fig. 1A, B). However, the major characteristic of this specimen lies in its p4, which is markedly compressed mesiodistally as is observed on the holotype. As in the latter, the metaconid is placed lingually to the protoconid and is not shifted posteriorly as is observed in Molinodus suarezi (Fig. 1D). Furthermore, the p4 of MHNC 13872 has the same strongly bulbous morphology as that of the holotype. The m1 is relatively worn but does not depart significantly from that of the holotype in terms of morphology. However, the two specimens differ in their size and the new specimen described here is distinctly smaller than the holotype (Table 2). As a matter of fact, the p4 and m1 of the new specimen are in average 10% smaller than those of the holotype (mean of the four ratios of Table 2). Although significant, this difference could be interpreted as related to individual size variation. The other large “condylarth” to which this specimen could be related is Molinodus suarezi, although this taxon is clearly smaller than Simoclaenus sylvaticus. However, the p4 observed on the mandible of M. suarezi described above (Fig. 2A) is so different from that of MHNC 13872 that we rather favor a strong individual size variation in S. sylvaticus than morphological variation in M. suarezi. A well-preserved lateral ascending process of a right maxilla (MHNC 13868) is referred to Simoclaenus sylvaticus. This specimen bears the root of the canine and the four premolars, which were unknown for this taxon (Fig. 8). The upper premolars of MHNC 13868 are only slightly larger than those of Molinodus suarezi described by Muizon & Cifelli (2000: 59), but this difference could be interpreted as related to individual variation in size. The major criterion that convinced us to relate this specimen to S. sylvaticus is the size of the canine. Although the crown of that tooth is not preserved the section of the root at the level of the alveolar border is relevant to its size. It is noteworthy that no upper canine is known for M. suarezi. We therefore compared the section of the upper canine of MHNC 13868 to that of the lower canine of MHNC 13883. Because the Tiupampa kollpaniines are relatively unspecialized, it is hypothesized that the width and length (at the level of the alveolar plane) of the upper and lower canines did not differ significantly even if generally the upper canines are slightly larger than the lowers. This remains an assumption, as no kollpaniine has ever been documented by both upper and lower canines. Here, the upper canine of MHNC 13868 (Simoclaenus) is 87% longer and 55% wider than the lower canine of MHNC 13883 (Molinodus) (Table 3). Even taking into account the approximation in comparing upper and lower canines, such a size difference is highly significant and we regard as unlikely that the two canines could belong to the same taxon of kollpaniine. We therefore, tentatively refer MHNC 13868 to S. sylvaticus rather than to M. suarezi. Furthermore, the size difference between the P4 and M1 of the holotype of S. sylvaticus and referred specimen described here could be related to sexual dimorphism in this species as evoked above. The premolars are well preserved and bear very reduced dental wear. The size of P3 and P4 is slightly larger than the equivalent teeth in Molinodus suarezi, which are known on one specimen only (MHNC 1247) (see Muizon & Cifelli 2000: 58) (Table 4). P1 and P2 are unknown for M. suarezi. Although this size difference is moderate (c. 10%), because of the large size of the canine, we rather refer this specimen to Simoclaenus sylvaticus. Furthermore, the anteroposterior length of the upper premolar row of MHNC 13868 (11.31 mm) is only slightly smaller than the lower premolar row of the holotype of S. sylvaticus (11.97 mm), on which the alveoli of p1-3 and the p4 are preserved. Therefore, the mesiodistal length of the upper premolar row of the new specimen (MHNC 13868) correctly matches the length of the lower premolars row of the holotype (MHNC 8348). P1 is peg-like, single-rooted, and compressed transversely. It is implanted vertically in the maxilla as is observed on the alveolus of the p1 of the holotype (MHNC 8348). This condition suggests a relative shortness of the rostrum and is congruent with the anteroposterior compression of the lower cheek teeth observed on the mandible. It is noteworthy that the p1 of Molinodus described above (MHNC 13883) differs from the condition observed in Simoclaenus in being slightly procumbent, thus suggesting a more elongated rostrum. As preserved, the P1 of Simoclaenus on MHNC 13868 is longer than high and no significant wear facet can be observed at the apex of its crown. In lateral view the tooth is roughly symmetrical anteroposteriorly. A small diastema separates P1 from the canine anteriorly and from P2 posteriorly. P2 is triangular in occlusal view and bears three roots. It is longer than wide. It presents a conspicuous inflation on its distolingual edge, which can be regarded as an incipiently developed protocone (protoconal bulge). The paracone forms most of the tooth and is as high as long. Its mesial edge is wide and blunt whereas its distal edge is thin and forms a sharp crest. The tooth bears no cingulum but a small cusp at the distolabial edge of the paracone could be regarded as a metastyle. This style contacts the anterior edge of P3 and no diastema separates the two teeth. P3 is slightly wider than long, triangular in occlusal view, and bears three roots. The mesial and distal edges are markedly concave, a condition which individualizes a well-developed protocone lingually. This cusp is approximately two thirds the height of the paracone. It is as long as wide. It has a very convex lingual edge and a flat labial aspect. These two edges of the tooth are separated by sharp pre- and postprotocristae, which join the base of the crown at the level of the greatest concavity of the mesial and distal edges of the tooth. Labially the paracone is approximately twice as long as wide. Its mesial edge bears a smooth crest and its distal crest is slightly obliterated by an elongated wear facet, which extends from the apex of the tooth to the posterior base of the paracone. At the mesial angle of the paracone is a marked parastyle. From this cusp, a conspicuous cingulum extends on labial edge of the paracone. At the distal end of the cingulum is a small metastyle. P4 has a pattern similar to that of P3 but it is mesiodistally shorter and transversely wider. Its mesial and distal edges are slightly concave but to a much lesser extent than the condition observed on P3. The paracone is smaller (in height and volume) and the protocone is more voluminous than on the preceding tooth. The pre- and postprotocristae are more developed than on P3 and extend on the anterior and posterior edges of the paracone. The postprotocrista even joins the distolabial angle of the tooth and contacts the postparacrista. The latter bears a narrow wear facet on its mesial two thirds only. The distal end of the postparacrista bears, on its lingual aspect, a hint of inflation, which can be interpreted as an incipient metacone. A tiny inflation on the postprotocrista may also be regarded as an incipient metaconule. On the distal edge of the protocone, is a distinct postcingulum. On its mesial edge the precingulum is weakly developed. On the mesiolabial angle of the tooth the parastyle is more developed than on P3. From this style, a well-developed labial cingulum extends distally until the metastylar angle of P4. Little is preserved of the palatal process of the maxilla, but the lateral wall of the rostrum from the anterior edge of the canine to the anterior root of the zygomatic arch is relatively complete and all its edges likely correspond to sutures with adjacent bones except for a small U-shaped-break in the posterodorsal angle (Fig. 8C). The anterodorsal edge of the specimen probably corresponds to the nasal-maxilla suture. Approximately above the P1-P2 embrasure, the edge of the maxilla distinctly protrudes medially. Anterior to this indentation, the suture is apparently anteroposteriorly oriented or slightly oriented anterolaterally. Posterior to it, the suture diverges posterolaterally, thus indicating a widening of the nasals posteriorly, as generally observed in early diverging metatherians and eutherians (e.g., deltatheroidans, pucadelphydans, Zalambdalestes, Kulbeckia, Alcidedorbignya). On the posterior limit of the maxilla, as preserved, is a deep groove probably for the articulation of the anterior process of the jugal. This groove (maxillajugal suture) approximately corresponds to the level of the anterior edge of the orbit and the posterior limit of the rostrum, which corresponds to the posterior edge of P4. On the posterodorsal angle of the specimen, in lateral view, is a distinct small notch (dorsal to the breakage notch mentioned above), which was receiving the anterolateral angle of the frontal. If this interpretation is correct, the nasal and lacrimal of Simoclaenus were distinctly separated, which likely represents a crown Placentalia condition (frontal-maxilla suture present) (Muizon et al. 2015). The posterior edge of the maxilla, between this notch and the dorsal end of the jugal groove, likely corresponds to the lacrimal-maxilla suture. Anteriorly, several grooves mark the edge of the maxilla immediately anterior to the canine, which we interpret as the premaxilla-maxilla suture. This suture is almost straight, slightly concave anteriorly, and sub-vertical, forming an angle of approximately 95° with the alveolar plane (Fig. 8C). The lateral aspect of the maxilla is markedly elevated and erected, to a greater extent than the condition observed in the pantodont Alcidedorbignya inopinata from the same locality (Muizon et al. 2015). This condition apparently resembles that of Baioconodon nordicum (YPM-PU 14234) from the earliest Palaeocene (Puercan) of Mantua lentil of Wyoming. The anterior opening of the infraorbital canal is 2.08 mm high and located above the mesiolabial root of P3. In this respect Simoclaenus differs from the condition in Maiorana and Baioconodon, in which the infraorbital foramen is located more posteriorly, above the mesiolabial root of P4. A condition similar to that of Maiorana and Baioconodon is observed in Didolodus multicuspis (MACN 10690), in which the infraorbital foramen is located above the distal edge of P3 and most of the P4 (Gelfo, personal communication). Anterior to this foramen is a tiny opening located above the anterior root of P2, and which probably represents a nutrient foramen. In its anterior region, the maxilla is not inflated laterally by the canine as is observed in Alcidedorbignya, due to the fact that the canine was compressed transversely. This condition particularly resembles the “condylarths” of Mantua lentil of Wyoming, Baioconodon and Maiorana. The third specimen referred to Simoclaenus sylvaticus is a partial maxilla with M1-2 (MHNC 13876), (Fig. 9). The M2 perfectly matches the size and morphology of that of MHNC 8348 described by Muizon & Cifelli (2000). The small differences between the two teeth are the presence, in MHNC 13876, of a slightly larger parastyle, a cuspule on the preparaconular crista located between the paraconule and the parastyle and a slight inflation of the lingual end of the precingulum (cuspule?). The M2 of MHNC 13876 has the characteristic asymmetrical morphology observed in Molinodus and Simoclaenus, in which the paracone is distinctly more labial than the metacone (Muizon & Cifelli 2000: fig. 2A-C, fig. 14C). This condition is not observed on the M1 of Molinodus, the paracone of which is not shifted labially. The most interesting characteristic of this specimen is in the relative wear stage of the M2 and M1. The M2 has a wear stage approximately similar to that of the M2 of MHNC 8348. In contrast the M1 is totally excavated in its lingual two thirds: the protocone, the protocristae and the conules, the pre-and postcingula, and the trigon basin have disappeared; the only preserved elements of the tooth are the para- and metacones, the styles and the labial cingulum. This wear stage is clearly more advanced than that observed on the M1 of MHNC 8348, in which the protocone and conules are coalescent but still identifiable, the protocristae and the pre-and postcingula are distinctly observable. This stage of wear of M2-1 of MHNC 8348 is comparable to that observed on the maxilla of Molinodus suarezi (MHNC 1247) described by Muizon & Cifelli (2000). In fact, the extensive wear of the M1 of MHNC 13876 is comparable to the condition that could be observed on a DP4, an interpretation impossible given the fact that the posterior tooth is undoubtedly an M2, which presents the characteristic asymmetrical morphology of that tooth (Muizon & Cifelli 2000). Furthermore, the roots of the M1 are long and the lingual root perforates the floor of the orbit, which suggests that it is not a deciduous molar. In ventral view, laterally to M2, the maxillar process of the zygoma and the anterior border of the orbitotemporal fossa are preserved. The latter is at the level of the apex of the metacone of M2, while it is at the level of the paracone of M3 on the maxilla (MHNC 8348) referred to Simoclaenus by Muizon & Cifelli (2000). In Molinodus the anterior edge of the orbitotemporal fossa is at the level of the paracone of M3 and in Baioconodon (YPM-PU 14234) and Maiorana (YPM-PU 16667 and 14171) it is at the level of the metacone of M3. However, this condition is likely to be individually variable since in Alcidedorbignya inopinata out of 13 specimens, in which it can be observed, three of them (see Muizon et al. 2015: fig. 10B) have an anterior edge of the orbitotemporal fossa at the level of the metacone of M2, as observed in the Simoclaenus specimen described here. In the other ten specimens, the anterior edge of the fossa is at the level of the paracone of M3. In the Alcidedorbignya sample the anterior position of M2 is observed in young adults and may be related to the ontogenetic increase of the length of the rostrum.

Tiuclaenus robustus Muizon & Cifelli, 2000 DIAGNOSIS. ��� See Muizon & Cifelli (2000). DESCRIPTION A right mandible fragment bearing m2-3 (MHNC 13875) has been referred to Tiuclaenus robustus (Fig. 10B, C) essentially because, although structurally similar to the other species of Tiuclaenus (T. minutus and T. cotasi), it differs from them in its size, distinctly larger, and in its greater massiveness. Furthermore, as is observed on the holotype (a mandible fragment with m2-m3, MHNC 1233), m3 of MHNC 13875 is proportionally shorter than in T. minutus and T. cotasi being barely longer than m2. An interesting feature of this specimen is the morphology of the roots of m2 and m3, which are long extending ventrally on more than 2.5 the height of the crown (Fig. 10C). Furthermore, the apices of the roots are markedly splayed with their posterior edges extending posteriorly, providing the extremity of the root a characteristic hammer-shape. Although the ventral edge of the dentary is partly broken, this morphology gives the impression that the root had to develop posteriorly because it was abutting the ventral edge of the mandibular canal., Published as part of Muizon, Christian de, Billet, Guillaume & Ladev��ze, Sandrine, 2019, New remains of kollpaniine " condylarths " (Panameriungulata) from the early Palaeocene of Bolivia shed light on hypocone origins and molar proportions among ungulate-like placentals, pp. 841-874 in Geodiversitas 41 (25) on page 856, DOI: 10.5252/geodiversitas2019v41a25, http://zenodo.org/record/3699898, {"references":["MUIZON C. DE & CIFELLI R. L. 2000. - The \" condylarths \" (archaic Ungulata, Mammalia) from the early Palaeocene of Tiupampa (Bolivia): implications on the origin of the South American ungulates. Geodiversitas 22 (1): 47 - 150."]}

Genus Mystacodon Lambert, Martínez-Cáceres, Bianucci, Di Celma, Salas- Gismondi, Steurbaut, Urbina & Muizon, 2017 TYPE AND ONLY SPECIES INCLUDED. — Mystacodon selenensis. ETYMOLOGY. — From ancient Greek mystacos (“moustache”) in reference to the suborder Mysticeti and odontos (“tooth”), “mysticete with teeth”. DIAGNOSIS. — The same as for the type species, Mystacodon selenensis., Published as part of Muizon, Christian de, Bianucci, Giovanni, Martínez-Cáceres, Manuel & Lambert, Olivier, 2019, Mystacodon selenensis, the earliest known toothed mysticete (Cetacea, Mammalia) from the late Eocene of Peru: anatomy, phylogeny, and feeding adaptations, pp. 401-499 in Geodiversitas 41 (11) on pages 405-406, DOI: 10.5252/geodiversitas2019v41a11, http://zenodo.org/record/3699733, {"references":["LAMBERT O., MARTINEZ- CACERES M., BIANUCCI G., DI CELMA C., SALAS- GISMONDI R., STEURBAUT E., URBINA M. & MUIZON C. DE 2017 a. - Earliest mysticete from the Late Eocene of Peru sheds new light on the origin of baleen whales. Current Biology 27 (10): 1535 - 1541. e 2. https: // doi. org / 10.1016 / j. cub. 2017.04.026"]}

Mystacodon selenensis Lambert, Martínez-Cáceres, Bianucci, Di Celma, Salas- Gismondi, Steurbaut, Urbina & Muizon, 2017 HOLOTYPE. — MUSM 1917, a partial skeleton. Associated elements include the skull, missing most of the basicranium and the right squamosal and jugal; a fragmentary left tympanic; both dentaries; thyrohyal; cervical and thoracic vertebrae; ribs; sternum (four elements, including manubrium and xiphisternum); partial right and left forelimbs; and left innominate. ETYMOLOGY. — From Selene, the Greek goddess of the moon, in reference to the Playa Media Luna, the type locality. TYPE LOCALITY. — The type specimen comes from the Playa Media Luna (14°36’7.2”S, 75°54’48W), close to the Pacific coast in the southern part of the Pisco Basin, at about the level of the km 400 of the South Panamerican Highway (Fig. 1). TYPE HORIZON AND AGE. — The holotype of Mystacodon selenensis MUSM 1917 was discovered in the middle part of the Yumaque Member of the Paracas Formation, 77 m above the contact with the Los Choros Member (Figs 2; 3) (see DeVries 2017 for a revised interpretation of the Eocene depositional sequence in the area). Layers of the Yumaque Member comprise finely laminated to massive, diatomacetous siltstones, containing pelagic microfossils, thin-shelled pectinid bivalves, and numerous fish scales; they represent deposition in distal (outer shelf), low-energy marine settings (Lambert et al. 2017a; DeVries 2017). The calcareous nannofossil investigation of 37 sediment samples from the Yumaque Member and the overlying lower part of the Otuma Formation, taken along the stratigraphic section in the type locality of Playa Media Luna, allowed positioning the type horizon in the lower part of calcareous nannofossil zone NP19/20 of Martini (1971); based on age estimations by Agnini et al. (2014), an age of 36.4 Ma (early Priabonian, early late Eocene) has been proposed (see Lambert et al. 2017a for more details). EMENDED DIAGNOSIS. — Mystacodon selenensis is identified as a Neoceti based on the following derived characters, absent in basilosaurid archaeocetes: partly open mesorostral groove; anteroposteriorly elongated rostral portion of maxilla; presence of an antorbital process of the maxilla; supraoccipital shield anterodorsally inclined; and distal epiphysis of the humerus divided in two angled radial and ulnar facets. Mystacodon selenensis is referred to the Mysticeti due to the following combination of derived characters: dorsoventrally thin posterolateral region of maxilla on rostrum; antorbital process of maxilla separated from lacrimal; presence of a maxillary infraorbital plate; apex of zygomatic process of squamosal closely apposed to postorbital process of frontal or situated ventral to the latter; external occipital crest restricted to anterodorsal half of supraoccipital shield; and triangular supraoccipital shield. Mystacodon selenensis differs from all other toothed mysticetes in bearing the following combination of features: 1) elongated nasal, the nasal being longer than the length of the frontal + parietal, at midline; 2) anteriorly located antorbital foramina, at about the level of the diastema between P2 and P3; 3) absence of real antorbital notch; 4) long jugo-squamosal suture, with an anterior prolongation of the zygomatic process of the squamosal, extending as far as the level of the postorbital process of the frontal anteriorly; 5) short anterior process of the frontal separating the posterior apices of the nasals; 6) sutured mandibular symphysis, the posterior edge of which is at the level of the i3-p1 diastema; and 7) ventral border of the mandibular ramus being slightly concave ventrally. Mystacodon selenensis also bears four additional derived characters: upturned (i.e., dorsally concave) anterior region of the rostrum; posteriormost upper tooth anterior to level of antorbital process of maxilla; broad-based rostrum (ratio between width of skull at rostrum base and width at postorbital process> 0.8); and strong tuberosity on anterior edge of radius (the latter condition is unknown in the other toothed mysticetes). Furthermore, Mystacodon selenensis bears a series of plesiomophic features: supraoccipital shield not extending anterior to anterior level of squamosal fossa; only two dorsal infraorbital foramina; a basilosaurid-like dental formula 3.1.4.2/3.1.4.3; no wide diastemata between posterior cheek teeth; sutured mandibular symphysis; and well-defined acetabulum on innominate. Mystacodon selenensis differs from Llanocetus denticrenatus in the following characters: 1) much smaller size (less than half the estimated body size); 2) rostrum narrower with concave edges while the preserved posterior part of the rostrum of Llanocetus is much wider and laterally expanded; 3) alveolar border of the maxilla on posterior region of the rostrum rounded dorsolaterally in cross-section with a subvertical lateral wall, while it is flat and crest-like in Llanocetus; 4) preserved parts of the palate lack deep lateral sulci, while they are distinctly present and abundant in Llanocetus; 5) premaxillae abruptly depressed just anterior to the nasals, while in Llanocetus the transition to the post narial part of the premaxillae is smooth; 6) upper molars closely approximated, while they are separated by large diastemata in Llanocetus; 7) upper molars much larger; 8) short diastema between P3 and P4 (less than one tooth mesiodistal length), while in Llanocetus the diastema is two to three times a tooth length; 9) much longer orbit; 10) nearly straight lateral edge of the supraorbital process, while it is deeply concave in Llanocetus; 11) posterior edge of the supraorbital process roughly straight, while it is concave in Llanocetus; 12) orbitotemporal crests extend posteriorly until anteroposterior mid-point of the parietals, while in Llanocetus they end anteriorly, at the posteromedial angle of the supraorbital process of the frontal; 13) dorsal edge of the parietals is subhorizontal in lateral view, while it ascends steeply toward the vertex in Llanocetus; 14) intertemporal bridge much narrower than long transversely, while it is as wide as long in Llanocetus; 15) anterior angle of nuchal crest posterior to anterior margin of squamosal fossa, while it approximately reaches the level of the middle of the fossae in Llanocetus; 16) lateral edges of the supraoccipital in dorsal view straight, while they are sigmoid in Llanocetus; 17) vertex and dorsal aspect of the braincase almost in the same plane as the posterior region of the rostrum, while in Llanocetus they slope anteriorly and distinctly overhang the rostrum; 18) distal extremity of anterior ribs expanded and pestle-like, while this condition is absent in Llanocetus. Mystacodon selenensis differs from Coronodon havensteini in having a longer rostrum and longer diastemata between the premolars; much longer nasals associated to more anterior bony nares, located in the anterior half of the rostrum (in the posterior third in Coronodon); temporal fossae more elongated anteroposteriorly; a long and thin (dorsoventrally) zygomatic process of the squamosal (short and stout in Coronodon); a sharp external occipital crest; a tightly articulated mandibular symphysis; and an sub-horizontal or gently sloping tooth wear on all preserved teeth with strong edges at the apical surface. In addition to its autapomorphies, Mystacodon selenensis differs from mammalodontids in having: a rostrum at least proportionally twice longer; much more anteriorly placed bony nares; a sharply triangular occipital shield; a well-developed external occipital crest (low, when present, in mammalodontids); a strong palatine sulcus on the medial edge of the premaxilla and maxilla anteriorly; much longer diastemata between the premolars; and absence of the markedly V-shaped fronto-parietal suture (as observed in mammalodontids). As compared with aetiocetids, Mystacodon selenensis has a basilosaurid-like dental formula; an almost horizontal apical tooth wear; much larger postcanine teeth; and a long and slender zygomatic process of the squamosal, which is lowest at its anteriormost portion. M. selenensis lacks all the aetiocetid characteristic features, such as the extreme dorsoventral compression of the rostrum; the deeply concave lateral edge of the supraorbital process of the frontal in dorsal view; the anteroposteriorly short zygomatic process of the squamosal (as compared to that of basilosaurids); and the very thin jugal. Otuma Formation Yumaque Member of the Paracas Formation Los Choros Member of the Paracas Formation Finally, Mystacodon selenensis lacks cranial synapomorphies of Odontoceti: facial concavity; presence of premaxillary foramen and premaxillary sac fossa; and wide posterior expansion of maxilla overlapping the supraorbital region.

Genus Mystacodon Lambert, Martínez-Cáceres, Bianucci, Di Celma, Salas- Gismondi, Steurbaut, Urbina & Muizon, 2017 TYPE AND ONLY SPECIES INCLUDED. — Mystacodon selenensis. ETYMOLOGY. — From ancient Greek mystacos (“moustache”) in reference to the suborder Mysticeti and odontos (“tooth”), “mysticete with teeth”. DIAGNOSIS. — The same as for the type species, Mystacodon selenensis.

Mystacodon selenensis Lambert, Martínez-Cáceres, Bianucci, Di Celma, Salas- Gismondi, Steurbaut, Urbina & Muizon, 2017 HOLOTYPE. — MUSM 1917, a partial skeleton. Associated elements include the skull, missing most of the basicranium and the right squamosal and jugal; a fragmentary left tympanic; both dentaries; thyrohyal; cervical and thoracic vertebrae; ribs; sternum (four elements, including manubrium and xiphisternum); partial right and left forelimbs; and left innominate. ETYMOLOGY. — From Selene, the Greek goddess of the moon, in reference to the Playa Media Luna, the type locality. TYPE LOCALITY. — The type specimen comes from the Playa Media Luna (14°36’7.2”S, 75°54’48W), close to the Pacific coast in the southern part of the Pisco Basin, at about the level of the km 400 of the South Panamerican Highway (Fig. 1). TYPE HORIZON AND AGE. — The holotype of Mystacodon selenensis MUSM 1917 was discovered in the middle part of the Yumaque Member of the Paracas Formation, 77 m above the contact with the Los Choros Member (Figs 2; 3) (see DeVries 2017 for a revised interpretation of the Eocene depositional sequence in the area). Layers of the Yumaque Member comprise finely laminated to massive, diatomacetous siltstones, containing pelagic microfossils, thin-shelled pectinid bivalves, and numerous fish scales; they represent deposition in distal (outer shelf), low-energy marine settings (Lambert et al. 2017a; DeVries 2017). The calcareous nannofossil investigation of 37 sediment samples from the Yumaque Member and the overlying lower part of the Otuma Formation, taken along the stratigraphic section in the type locality of Playa Media Luna, allowed positioning the type horizon in the lower part of calcareous nannofossil zone NP19/20 of Martini (1971); based on age estimations by Agnini et al. (2014), an age of 36.4 Ma (early Priabonian, early late Eocene) has been proposed (see Lambert et al. 2017a for more details). EMENDED DIAGNOSIS. — Mystacodon selenensis is identified as a Neoceti based on the following derived characters, absent in basilosaurid archaeocetes: partly open mesorostral groove; anteroposteriorly elongated rostral portion of maxilla; presence of an antorbital process of the maxilla; supraoccipital shield anterodorsally inclined; and distal epiphysis of the humerus divided in two angled radial and ulnar facets. Mystacodon selenensis is referred to the Mysticeti due to the following combination of derived characters: dorsoventrally thin posterolateral region of maxilla on rostrum; antorbital process of maxilla separated from lacrimal; presence of a maxillary infraorbital plate; apex of zygomatic process of squamosal closely apposed to postorbital process of frontal or situated ventral to the latter; external occipital crest restricted to anterodorsal half of supraoccipital shield; and triangular supraoccipital shield. Mystacodon selenensis differs from all other toothed mysticetes in bearing the following combination of features: 1) elongated nasal, the nasal being longer than the length of the frontal + parietal, at midline; 2) anteriorly located antorbital foramina, at about the level of the diastema between P2 and P3; 3) absence of real antorbital notch; 4) long jugo-squamosal suture, with an anterior prolongation of the zygomatic process of the squamosal, extending as far as the level of the postorbital process of the frontal anteriorly; 5) short anterior process of the frontal separating the posterior apices of the nasals; 6) sutured mandibular symphysis, the posterior edge of which is at the level of the i3-p1 diastema; and 7) ventral border of the mandibular ramus being slightly concave ventrally. Mystacodon selenensis also bears four additional derived characters: upturned (i.e., dorsally concave) anterior region of the rostrum; posteriormost upper tooth anterior to level of antorbital process of maxilla; broad-based rostrum (ratio between width of skull at rostrum base and width at postorbital process> 0.8); and strong tuberosity on anterior edge of radius (the latter condition is unknown in the other toothed mysticetes). Furthermore, Mystacodon selenensis bears a series of plesiomophic features: supraoccipital shield not extending anterior to anterior level of squamosal fossa; only two dorsal infraorbital foramina; a basilosaurid-like dental formula 3.1.4.2/3.1.4.3; no wide diastemata between posterior cheek teeth; sutured mandibular symphysis; and well-defined acetabulum on innominate. Mystacodon selenensis differs from Llanocetus denticrenatus in the following characters: 1) much smaller size (less than half the estimated body size); 2) rostrum narrower with concave edges while the preserved posterior part of the rostrum of Llanocetus is much wider and laterally expanded; 3) alveolar border of the maxilla on posterior region of the rostrum rounded dorsolaterally in cross-section with a subvertical lateral wall, while it is flat and crest-like in Llanocetus; 4) preserved parts of the palate lack deep lateral sulci, while they are distinctly present and abundant in Llanocetus; 5) premaxillae abruptly depressed just anterior to the nasals, while in Llanocetus the transition to the post narial part of the premaxillae is smooth; 6) upper molars closely approximated, while they are separated by large diastemata in Llanocetus; 7) upper molars much larger; 8) short diastema between P3 and P4 (less than one tooth mesiodistal length), while in Llanocetus the diastema is two to three times a tooth length; 9) much longer orbit; 10) nearly straight lateral edge of the supraorbital process, while it is deeply concave in Llanocetus; 11) posterior edge of the supraorbital process roughly straight, while it is concave in Llanocetus; 12) orbitotemporal crests extend posteriorly until anteroposterior mid-point of the parietals, while in Llanocetus they end anteriorly, at the posteromedial angle of the supraorbital process of the frontal; 13) dorsal edge of the parietals is subhorizontal in lateral view, while it ascends steeply toward the vertex in Llanocetus; 14) intertemporal bridge much narrower than long transversely, while it is as wide as long in Llanocetus; 15) anterior angle of nuchal crest posterior to anterior margin of squamosal fossa, while it approximately reaches the level of the middle of the fossae in Llanocetus; 16) lateral edges of the supraoccipital in dorsal view straight, while they are sigmoid in Llanocetus; 17) vertex and dorsal aspect of the braincase almost in the same plane as the posterior region of the rostrum, while in Llanocetus they slope anteriorly and distinctly overhang the rostrum; 18) distal extremity of anterior ribs expanded and pestle-like, while this condition is absent in Llanocetus. Mystacodon selenensis differs from Coronodon havensteini in having a longer rostrum and longer diastemata between the premolars; much longer nasals associated to more anterior bony nares, located in the anterior half of the rostrum (in the posterior third in Coronodon); temporal fossae more elongated anteroposteriorly; a long and thin (dorsoventrally) zygomatic process of the squamosal (short and stout in Coronodon); a sharp external occipital crest; a tightly articulated mandibular symphysis; and an sub-horizontal or gently sloping tooth wear on all preserved teeth with strong edges at the apical surface. In addition to its autapomorphies, Mystacodon selenensis differs from mammalodontids in having: a rostrum at least proportionally twice longer; much more anteriorly placed bony nares; a sharply triangular occipital shield; a well-developed external occipital crest (low, when present, in mammalodontids); a strong palatine sulcus on the medial edge of the premaxilla and maxilla anteriorly; much longer diastemata between the premolars; and absence of the markedly V-shaped fronto-parietal suture (as observed in mammalodontids). As compared with aetiocetids, Mystacodon selenensis has a basilosaurid-like dental formula; an almost horizontal apical tooth wear; much larger postcanine teeth; and a long and slender zygomatic process of the squamosal, which is lowest at its anteriormost portion. M. selenensis lacks all the aetiocetid characteristic features, such as the extreme dorsoventral compression of the rostrum; the deeply concave lateral edge of the supraorbital process of the frontal in dorsal view; the anteroposteriorly short zygomatic process of the squamosal (as compared to that of basilosaurids); and the very thin jugal. Otuma Formation Yumaque Member of the Paracas Formation Los Choros Member of the Paracas Formation Finally, Mystacodon selenensis lacks cranial synapomorphies of Odontoceti: facial concavity; presence of premaxillary foramen and premaxillary sac fossa; and wide posterior expansion of maxilla overlapping the supraorbital region., Published as part of Muizon, Christian de, Bianucci, Giovanni, Martínez-Cáceres, Manuel & Lambert, Olivier, 2019, Mystacodon selenensis, the earliest known toothed mysticete (Cetacea, Mammalia) from the late Eocene of Peru: anatomy, phylogeny, and feeding adaptations, pp. 401-499 in Geodiversitas 41 (11) on pages 406-407, DOI: 10.5252/geodiversitas2019v41a11, http://zenodo.org/record/3699733, {"references":["DEVRIES T. J. 2017. - Eocene stratigraphy and depositional history near Puerto Caballas (East Pisco Basin, Peru). Boletin de la Sociedad Geologica del Peru 112: 39 - 52.","LAMBERT O., MARTINEZ- CACERES M., BIANUCCI G., DI CELMA C., SALAS- GISMONDI R., STEURBAUT E., URBINA M. & MUIZON C. DE 2017 a. - Earliest mysticete from the Late Eocene of Peru sheds new light on the origin of baleen whales. Current Biology 27 (10): 1535 - 1541. e 2. https: // doi. org / 10.1016 / j. cub. 2017.04.026","MARTINI E. 1971. - Standard Tertiary and Quaternary calcareous nannoplankton zonation. Proceedings of Second Planktonic Conference, Roma, 1970, 2: 739 - 785.","AGNINI C., FORNACIARI E., RAFFI I., CATANZARITI R., PALIKE H., BACKMAN J. & RIO D. 2014. - Biozonation and biochronology of Paleogene calcareous nannofossils from low and middle latitudes. Newsletters on Stratigraphy 47: 131 - 181. https: // doi. org / 10.1127 / 0078 - 0421 / 2014 / 0042"]}

Genus Africanacetus Bianucci, Lambert & Post, 2007 TYPE SPECIES. ��� Africanacetus ceratopsis Bianucci, Lambert & Post, 2007 by original designation. OTHER REFERRED SPECIES. ��� Africanacetus gracilis Ichishima, Augustin, Toyofuku & Kitazato, 2017., Published as part of Lambert, Olivier, Muizon, Christian de, Duhamel, Guy & Plicht, Johannes Van Der, 2018, Neogene and Quaternary fossil remains of beaked whales (Cetacea, Odontoceti, Ziphiidae) from deep-sea deposits off Crozet and Kerguelen islands, Southern Ocean, pp. 135-160 in Geodiversitas 40 (6) on page 143, DOI: 10.5252/geodiversitas2018v40a6, http://zenodo.org/record/5745694, {"references":["BIANUCCI G., LAMBERT O. & POST K. 2007. - A high diversity in fossil beaked whales (Odontoceti, Ziphiidae) recovered by trawling from the sea floor off South Africa. Geodiversitas 29: 5 - 62.","ICHISHIMA H., AUGUSTIN A. H., TOYOFUKU T. & KITAZATO H. 2017. - A new species of Africanacetus (Odontoceti: Ziphiidae) found on the deep ocean floor off the coast of Brazil. Deep Sea Research Part II. https: // doi. org / 10.1016 / j. dsr 2.2016.12.002"]}

Genus Izikoziphius Bianucci, Lambert & Post, 2007 TYPE SPECIES. ��� Izikoziphius rossi Bianucci, Lambert & Post, 2007 by original designation. OTHER REFERRED SPECIES. ��� Izikoziphius angustus Bianucci, Lambert & Post, 2007., Published as part of Lambert, Olivier, Muizon, Christian de, Duhamel, Guy & Plicht, Johannes Van Der, 2018, Neogene and Quaternary fossil remains of beaked whales (Cetacea, Odontoceti, Ziphiidae) from deep-sea deposits off Crozet and Kerguelen islands, Southern Ocean, pp. 135-160 in Geodiversitas 40 (6) on page 149, DOI: 10.5252/geodiversitas2018v40a6, http://zenodo.org/record/5745694, {"references":["BIANUCCI G., LAMBERT O. & POST K. 2007. - A high diversity in fossil beaked whales (Odontoceti, Ziphiidae) recovered by trawling from the sea floor off South Africa. Geodiversitas 29: 5 - 62."]}

Genus Khoikhoicetus Bianucci, Lambert & Post, 2007 TYPE SPECIES. ��� Khoikhoicetus agulhasis Bianucci, Lambert & Post, 2007 by original designation. OTHER SPECIES INCLUDED. ��� Khoikhoicetus kergueleni n. sp., Published as part of Lambert, Olivier, Muizon, Christian de, Duhamel, Guy & Plicht, Johannes Van Der, 2018, Neogene and Quaternary fossil remains of beaked whales (Cetacea, Odontoceti, Ziphiidae) from deep-sea deposits off Crozet and Kerguelen islands, Southern Ocean, pp. 135-160 in Geodiversitas 40 (6) on page 138, DOI: 10.5252/geodiversitas2018v40a6, http://zenodo.org/record/5745694, {"references":["BIANUCCI G., LAMBERT O. & POST K. 2007. - A high diversity in fossil beaked whales (Odontoceti, Ziphiidae) recovered by trawling from the sea floor off South Africa. Geodiversitas 29: 5 - 62."]}

Genus Xhosacetus Bianucci, Lambert & Post, 2007 TYPE AND ONLY REFERRED SPECIES. ��� Xhosacetus hendeysi Bianucci, Lambert & Post, 2007 by original designation., Published as part of Lambert, Olivier, Muizon, Christian de, Duhamel, Guy & Plicht, Johannes Van Der, 2018, Neogene and Quaternary fossil remains of beaked whales (Cetacea, Odontoceti, Ziphiidae) from deep-sea deposits off Crozet and Kerguelen islands, Southern Ocean, pp. 135-160 in Geodiversitas 40 (6) on page 153, DOI: 10.5252/geodiversitas2018v40a6, http://zenodo.org/record/5745694, {"references":["BIANUCCI G., LAMBERT O. & POST K. 2007. - A high diversity in fossil beaked whales (Odontoceti, Ziphiidae) recovered by trawling from the sea floor off South Africa. Geodiversitas 29: 5 - 62."]}

Pontogeneus priscus Leidy, 1852 HOLOTYPE. — ANSP 13668, isolated middle cervical centrum. TYPE LOCALITY AND HORIZON. — The original description indicates that the holotype is "from the Eocene formation of Ouachita, Louisiana " (Leidy 1852: 52). Recently, Uhen (2005) pointed out the possibility that it comes from the vicinity of the Caldwell Parish, Louisiana, where the upper Eocene Jackson Group (Eargle 1959) is exposed. DISCUSSION Leidy (1852) created the taxon Pontogeneus priscus based on an isolated cervical vertebra (Fig. 4), figured by Kellogg (1936) and interpreted as a fifth cervical. Uhen (2005) recognized it as a more anterior cervical (C3 or C4) and considered both genus and species as nomina nuda because the original description was not diagnostic and the vertebra could belong to a small specimen of Basilosaurus (indeed, the centrum is quite similar in size to that of UM-WH74, a small Basilosaurus isis). However, it can be evaluated that the vertebarterial foramina in the holotype of P. priscus are proportionally larger than in Basilosaurus (Fig. 4). Such a feature is diagnostic for the genus Cynthiacetus (Martínez-Cáceres & Muizon 2011). Because of this character Pontogeneus priscus could have closer affinities with Cynthiacetus than with Basilosaurus (as proposed by Gingerich 2015). However, such a holotype (the centrum of an isolated cervical vertebra) is not regarded as diagnostic enough to characterize a basilosaurid taxon and it is suggested here that the binome Pontogeneus priscus should only refer to the cervical vertebra described by Leidy (1852). Therefore, the genus name and the species name should be regarded as a Basilosauridae or a Pelagiceti incertae sedis and restricted to the type specimen of P. priscus., Published as part of Martínez-Cáceres, Manuel, Lambert, Olivier & Muizon, Christian de, 2017, The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru, pp. 7-163 in Geodiversitas 39 (1) on page 13, DOI: 10.5252/g2017n1a1, http://zenodo.org/record/4535622, {"references":["LEIDY J. 1852. - Description of Pontogeneus priscus. Proceedings of the Academy of Natural Sciences of Philadelphia 6: 52.","UHEN M. D. 2005. - A new genus and species of archaeocete whale from Mississippi. Southeastern Geology 43 (3): 157 - 172.","KELLOGG R. 1936. - A review of the Archaeoceti. Carnegie Institution of Washington Publications 482: 1 - 366.","GINGERICH P. D. 2015. - New partial skeleton and relative brain size in the Late Eocene archaeocete Zygorhiza kochii (Mammalia, Cetacea) from the Pachuta Marl of Alabama, with a note on contemporaneous Pontogeneus brachyspondylus. Contributions from the Museum of Paleontology, University of Michigan 32: 161 - 188. http: // hdl. handle. net / 2027.42 / 113064"]}

Cynthiacetus maxwelli Uhen, 2005 Zeuglodon cf. brachyspondylus – Müller 1849: 26-28. — Kellogg 1936: 248 (in part). HOLOTYPE. — MMNS VP 445. It includes a partially preserved skull, dentaries, upper and lower dentitions, petro-tympanic complex, humerus, radius, ulna, cervical, thoracic and lumbar vertebrae. TYPE LOCALITY. — Cynthia Clay Pit, Hinds County, Mississippi, USA. TYPE HORIZON. — Yazoo Clay Formation, Priabonian, late Eocene. EMENDED DIAGNOSIS. — Cynthiacetus maxwelli differs mainly from C. peruvianus in having one more cusp on both mesial and distal edges on p3 and p4 (5 and 6 denticles respectively in p3 and p4). It also possesses a longer and lower dome-shaped neural arch on the atlas and shorter and more massive humerus, radius and ulna (cf. below)., Published as part of Martínez-Cáceres, Manuel, Lambert, Olivier & Muizon, Christian de, 2017, The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru, pp. 7-163 in Geodiversitas 39 (1) on page 16, DOI: 10.5252/g2017n1a1, http://zenodo.org/record/4535622, {"references":["UHEN M. D. 2005. - A new genus and species of archaeocete whale from Mississippi. Southeastern Geology 43 (3): 157 - 172.","MULLER J. 1849. - Uber die fossilen Reste der Zeuglodonten von Nordamerica, mit Rucksicht auf die europaischen Reste aus dieser Familie. G. Reimer, Berlin, 38 p.","KELLOGG R. 1936. - A review of the Archaeoceti. Carnegie Institution of Washington Publications 482: 1 - 366."]}

Genus Masracetus Gingerich, 2007 TYPE SPECIES. — Masracetus markgrafi Gingerich, 2007 by original designation., Published as part of Martínez-Cáceres, Manuel, Lambert, Olivier & Muizon, Christian de, 2017, The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru, pp. 7-163 in Geodiversitas 39 (1) on page 15, DOI: 10.5252/g2017n1a1, http://zenodo.org/record/4535622, {"references":["GINGERICH P. D. 2007. - Stromerius nidensis, new archaeocete (Mammalia, Cetacea) from the upper Eocene Qasr El-Sagha Formation, Fayum, Egypt. Contributions from the Museum of Paleontology, University of Michigan 31 (13): 363 - 378. http: // hdl. handle. net / 2027.42 / 57499"]}

Martínez-Cáceres, Manuel, Lambert, Olivier, Muizon, Christian de (2017): The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru. Geodiversitas 39 (1): 7-163, DOI: 10.5252/g2017n1a1, URL: http://dx.doi.org/10.5252/g2017n1a1

Genus Pontogeneus Leidy, 1852 TYPE SPECIES. — Pontogeneus priscus Leidy, 1852., Published as part of Martínez-Cáceres, Manuel, Lambert, Olivier & Muizon, Christian de, 2017, The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru, pp. 7-163 in Geodiversitas 39 (1) on page 13, DOI: 10.5252/g2017n1a1, http://zenodo.org/record/4535622, {"references":["LEIDY J. 1852. - Description of Pontogeneus priscus. Proceedings of the Academy of Natural Sciences of Philadelphia 6: 52."]}

Masracetus markgrafi Gingerich, 2007 Zeuglodon isis Stromer, 1908: 128 (in part). Zeuglodon cf. brachyspondylus Müller, 1849:26-28. — Stromer 1908: 136. — Kellogg 1936: 262. — Slijper 1936: 319. Cynthiacetus maxwelli Uhen, 2005: 160 (in part). HOLOTYPE. — SMNS 11414, vertebral column, part of specimen 'St. 8' in Stromer (1908: 129). The associated skull is catalogued as SMNS 11413. TYPE LOCALITY AND HORIZON. — Uhen (2005) pointed out that SMNS 11414 and SMNS 11413 could come from the Gehannam Formation (Bartonian) of the Fayum Province, Egypt. However, Gingerich (2007) follows Kellogg (1936) and indicates that the holotype of M. markgrafi comes from the Birket Qarun Formation, in the vicinity of Dimeh, also in the Fayum Province. This formation is regarded as early Priabonian in age by Gingerich (1992). DIAGNOSIS. — Large basilosaurid lacking the vertebral elongation observed in Basilosaurus. Masracetus is slightly larger than Cynthiacetus with a lower lumbar length-to-width ratio Llum / Wlum (Gingerich 2007). DISCUSSION The holotype of Masracetus markgrafi was initially referred to Z. brachyspondylus (Stromer 1908) and more recently to C. maxwelli (Uhen 2005). Gingerich (2007) pointed out that Masracetus differs from other basilosaurids in the size and proportions of its lumbar vertebrae. Based on this feature, Gingerich (2007) hypothesizes that Pontogeneus brachyspondylus could be referred to Masracetus. Because a comparison of lumbar ratios in a large sampling of basilosaurid specimens (Table 2) does not clearly distinguish Cynthiacetus from Masracetus, the differences between the two genera could very well represent intra-specific variation (when compared to the variation observed in D. atrox and Z. kochii). Until study of the most complete specimen of M. markgrafi (collected in 2006: Gingerich 2007) clarifies the validity of both Masracetus and M. markgrafi, we follow Gingerich (2007) and regard M. markragi as a different species from Cynthiacetus spp., Published as part of Martínez-Cáceres, Manuel, Lambert, Olivier & Muizon, Christian de, 2017, The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru, pp. 7-163 in Geodiversitas 39 (1) on page 15, DOI: 10.5252/g2017n1a1, http://zenodo.org/record/4535622, {"references":["GINGERICH P. D. 2007. - Stromerius nidensis, new archaeocete (Mammalia, Cetacea) from the upper Eocene Qasr El-Sagha Formation, Fayum, Egypt. Contributions from the Museum of Paleontology, University of Michigan 31 (13): 363 - 378. http: // hdl. handle. net / 2027.42 / 57499","STROMER E. 1908. - Die Archaeoceti des agyptischen Eozans. Beitrage zur Palaontolgie und Geologie Ostrerreich- Ungarns und des Orients 21: 106 - 178.","MULLER J. 1849. - Uber die fossilen Reste der Zeuglodonten von Nordamerica, mit Rucksicht auf die europaischen Reste aus dieser Familie. G. Reimer, Berlin, 38 p.","KELLOGG R. 1936. - A review of the Archaeoceti. Carnegie Institution of Washington Publications 482: 1 - 366.","SLIJPER E. J. 1936. - Die Cetaceen. Capita Zoologica 7: 1 - 590.","UHEN M. D. 2005. - A new genus and species of archaeocete whale from Mississippi. Southeastern Geology 43 (3): 157 - 172.","GINGERICH P. D. 1992. - Marine mammals (Cetacea and Sirenia) from the Eocene of Gebel Mokattam and Fayum, Egypt: stratigraphy, age, and paleoenvironments. University of Michigan Papers on Paleontology 30: 1 - 84. http: // hdl. handle. net / 2027.42 / 48630"]}

Genus Alcidedorbignya Muizon & Marshall, 1987 TYPE SPECIES. — Alcidedorbignya inopinata. DIAGNOSIS. — Because the genus is monospecific, its diagnosis is that of the type species., Published as part of Muizon, Christian de, Billet, Guillaume, Argot, Christine, Ladevèze, Sandrine & Goussard, Florent, 2015, Alcidedorbignya inopinata, a basal pantodont (Placentalia, Mammalia) from the early Palaeocene of Bolivia: anatomy, phylogeny and palaeobiology, pp. 397-634 in Geodiversitas 37 (4) on page 410, DOI: 10.5252/g2015n4a1, http://zenodo.org/record/5210632

Alcidedorbignya inopinata Muizon & Marshall, 1987 Alcidedorbignya inopinata Muizon & Marshall, 1987c: 205. HOLOTYPE. — A partial maxilla with P4-M3 (YPFB Pal 6121). HYPODIGM. — The hypodigm is that given in Muizon & Marshall (1992), to which we add the following specimens: MHNC 8372, an almost complete skeleton, which is missing only the left upper incisors, the two i1s, a few phalanges and some carpal and tarsal bones and a few caudal vertebrae; MHNC 8373, a partial skull with complete braincase and mandibles of a very young individual, possibly a near-term foetus or a new-born individual (some postcranial elements are preserved); MHNC 8399, a partial skull with the braincase and basicranium perfectly preserved; the rostrum has been partly weathered and part of the left maxilla and the dorsal bones of the rostrum are missing; the right maxilla and premaxilla and the dentaries are almost complete; the specimen also includes half of the atlas; MHNC 8416, a partial skull (with crushed basicranium but the two petrosals well-preserved) and mandibles of a juvenile individual, with a partial right limb, and some ribs; MHNC 8423 a partial skull and mandibles of a juvenile missing part of the occipital region and bearing right dC, erupting P1s, DP2s-DP4s, erupting M1s; di2s, right di3, dcs, p1s in crypt, dp2s-dp4s, and erupting m1s; MHNC 8400, a left maxilla (with C-M3) with jugal and lacrimal; MHNC 8401 a right maxilla with roots of C-P2 and P3-M3; MHNC 8402, associated left maxilla and dentary, with P1-M3 and p3-m3; MHNC 8403, associated right maxilla and dentary, with C-M3 and right i2-trigonid of m3 and left i1-C; MHNC 8404, left maxilla with P3-M3; MHNC 8405, left maxilla with root of canine and P1-M3; MHNC 8406 left maxilla with root of P2 and P3-M3; MHNC 8407, left maxilla with roots of P4, partial M1 and M2-M3; MHNC 8408, maxilla with P4-M1 and partial M2; MHNC 8409, right dentary with c-m3, MHNC 8410, fragment of left dentary with trigonid of m2 and m3; MHNC 8411, fragment of right dentary with m2-m3; MHNC 8412, fragment of right dentary with m2-m3; MHNC 8413, fragment of left dentary with talonid of m2 and m3; MHNC 8414, left dentary with roots of p3-m1 and weathered m2-m3; MHNC 8415, m3; MHNC 8359; right periotic; MHNC 8360, left periotic; MHNC 8361, right periotic; MHNC 8362, left periotic; MHNC 8419, right periotic; MHNC 8420, right periotic; MHNC 8421, left periotic; MHNC 8422, right periotic (pars cochlearis); MHNC 8423, a sub-complete skull and mandibles of a juvenile, missing most of the occipital and the premaxillae. GEOLOGICAL SETTING AND AGE. — The Tiupampa mammals occur in the middle section of the Santa Lucia Formation (Marshall et al. 1997). This section has been referred to the early Palaeocene by Gayet et al. (1992), Bonaparte et al. (1993), and Muizon (1998). However, an early late Palaeocene age has been suggested by Marshall et al. (1997) and Pascual & Ortiz-Jaureguizar (2007). Recently, Gelfo et al. (2009) have reassessed the age of the Tiupampa mammal fauna and concluded that it is of early Palaeocene age. The Tiupampa mammal-bearing beds are regarded by these authors as a probable equivalent of the late Puercan (Pu3) of North America and would therefore be as old as 64 to 64.5 Ma. This hypothesis is based on the fact that the Tiupampa mammal-bearing beds are included in a single reversed stratigraphic series, which is likely to correspond to Chron 28r (see Gelfo et al. 2009 for discussion). However, when Gelfo et al. (2009) wrote their paper, the reference for calibration of Chron 28r was Lofgren et al. (2004), and the correlation was with the late Puercan (Pu3). New dates and calibration of the NALMAs have slightly modified the age and position of Chron 28r. According to Wilson (2013, 2014) and Sprain et al. (2014) Chron 28r is totally included in the base of the early Torrejonian (To1) and its absolute age is bracketed between c. 65 Ma and 64.866. This represents the very base of the early Torrejonian (To1), which spans from 65.118 Ma to c. 63.5 Ma. In other words, the absolute age for the Tiupampa fauna is c. 65 Ma. EMENDED DIAGNOSIS This following extensive diagnosis presents a list of the major morphological features of the skeleton and teeth of Alcidedorbignya inopinata and represents, in fact, a summarized description. Below a differential diagnosis is also provided. General morphology Small size by pantodonts standards; tail, long, 70% of the head and body length. Teeth Dental formula I3/3, C1/1, P4/4, M3/3; incisors spatulate; I1 distinctly smaller than I2-3; contralateral I1s widely separated from each other; i1 i3; C and c large, protruding, splayed labially; P1-2 and p1-2 single rooted and proodont (i.e. single elevated cusp); P3-4 and p3-4 semimolariform; P3-4 with strongly V-shaped paracone and protocone (double V-shaped); M1-3 with distinct pre- and postcingula; paraconule well developed; metaconule weak to indistinct; protocone anteroposteriorly broad; paracone and metacone separated at base (i.e. not connate); M1 with paracone and metacone subequal in size; M2 with paracone slightly higher than metacone; M3 with paracone distinctly higher and much more voluminous than metacone; M1-2 with moderately dilambdodont ectoloph (i.e. slightly V-shaped centrocrista); well-developed wing-like preparacrista (including parastyle) and postmetacrista (including metastyle); well-developed stylar shelf approximately 30% of tooth width on M2; no mesostyle; M3 with wing-like preparacrista (including parastyle) and virtually no postmetacrista; lower molars increase in size posteriorly with m1 distinctly smaller than m2; trigonids wider than talonids; protoconid and metaconid subequal in size, paraconid smaller; antero- and posterocingulid weakly developed; talonid basined; m3 talonid elongate. Skull Dome-shaped skull in lateral view, with the nasals sloping anteriorly; greatest width of the skull at the level of the posterior root of the zygomatic arch, slightly anterior to the level of the anterior edge of the dentary-squamosal articulation; rostrum approximately twice as wide at base (level of the anterior edge of the orbits) as at apex; in dorsal view nasals distinctly wider posteriorly; frontal-parietal suture on sagittal plane located at mid-length of the skull; numerous foramina for temporal rami on the parietal and at the parietal-squamosal suture; small sagittal crest; bilobate nuchal crest strongly protruding posteriorly; palate narrow (less than two M2 widths); long parallel-sided basipharyngeal canal (approximately 20% of the total length of the skull); large triangular ectopterygoid process of the alisphenoid; small posterior opening of the alisphenoid canal opening just anterior to the foramen ovale; anterior end of the canal opening internally just posterior to the foramen rotundum; foramen rotundum and sphenorbital fissure separated but adjacent one to the other and opening anteriorly in the same common fossa; large ascending process of the palatine in the orbit; large descending process of the frontal posterior to the palatine process; maxilla does not contribute to the lateral wall of the skull; two large diploic frontal foramina above the orbit; double lacrimal foramen; large wing of the lacrimal on face; jugal-maxilla suture bifurcated; jugal-lacrimal contact; zygomatic arch relatively slender; postglenoid process narrow and elevated (more elevated than wide), approximately half the transverse width of the glenoid cavity; postglenoid foramen on the medial edge of postglenoid process; presence of a tubercle (postglenoid eminence) on the posteromedial edge of the foramen; relatively flat promontorium with a distinct sigmoid groove for the internal carotid artery; promontorium totally separated from the alisphenoid, basioccipital and basisphenoid; deep notch for the internal carotid artery in the posterolateral angle of the basisphenoid; apex of the promontorium truncated; epitympanic recess opened ventrally and formed by the squamosal laterally and the petrosal medially; large foramen for the ramus superior of the stapedial artery opening in the petrosal; triangular post-promontorial tympanic sinus posterior to the external aperture of the cochlear fossula; spur-like medial caudal tympanic process on posterior angle of postpromontorial tympanic sinus; conical subarcuate fossa; vestigial anterior lamina of the petrosal; presence of an intracranial cavity (the petrosquamosal fossa) for the passage of the ramus superior of the stapedial artery and its tributary vessels and, capsuloparietal emissary vein and tributaries; long and deep groove on cerebral face of the braincase for the orbitotemporal artery and vein; large mastoid exposure on occiput; large post-temporal foramen in the squamosal petrosal suture; ectotympanic horseshoe-shaped, with distinct styliform process ventrally; anterior crus of the ectotympanic with a double articulation with squamosal laterally and petrosal medially. Dentary Stout body with a roughly constant height; symphysis fused in adults; ramus triangular with a large masseteric fossa, coronoid process recurved posteriorly and almost as wide at apex as at base; strong and salient coronoid crest at anterior border of masseteric fossa; condyloid process well above occlusal plane; angular process extends posterior to the level of the condyle; angular process hook-like but robust and almost as long as high; anteroposteriorly oriented crest on medial face of the angular process for the insertion of the pterygoideus medialis. Postcranial skeleton Axis with anteroposteriorly elongated neural process; 13 thoracic vertebrae, 9 lumbar vertebrae, 4 sacral vertebrae, and approximately 18 caudal vertebrae; long neural processes of the thoracic vertebrae; scapula with a large triangular supraspinatus fossa and a narrow and deep infraspinatus fossa; spine elevated; acromion anteriorly and distally projected; humerus with greater tubercle slightly higher than the head; deltopectoral crest limited to proximal half of the bone; very robust, long, and medially projecting medial epicondyle; well-developed epicondylar ridge; medial crest of the humeral trochlea projecting more distally than the lateral; ulna bent anteriorly and medially; deep fossa for the flexor muscles on medial face of olecranon and diaphysis; trochlear notch wide open; angle between humeral and radial facets (in anterodistal view) obtuse; radius with ovalshaped proximal epiphysis; centrale present; five anterior digits with short metacarpals; no size reduction of any digit; ungual phalanges with robust palmar tubercle; innominate with a distinctly everted ilium and a ventrolaterally deflected anteroventral spine; acetabulum relatively shallow and open; femur with a spherical head; greater trochanter as high as the head; lesser trochanter triangular, blade-like, and posteromedially oriented; small third trochanter; distal epiphysis as wide as deep; tibia with a salient tibial crest and tubercle; fibula with a well-developed interosseous crest on its proximal half; tibial trochlea on the astragalus relatively flat and angle between the medial and lateral tibial facets more than 120°; angle between lateral tibial facet and fibular facet close to 90°; astragalus with a distinct cuboid facet on the head; calcaneofibular facet present on the calcaneus lateral to ectal facet; well-developed peroneal process of the calcaneus; calcaneus with a strongly oblique (in dorsal view) cuboid facet, which faces distolaterally; presence of a supplementary articular facet for the astragalus on the medial edge of the cuboid facet; five pedal digits slightly longer than the manual ones, ungual phalanges cleft, with distal half expanded transversely (scutiform) in dorsal view and deflected palamarly or plantarly in lateral view, with robust plantar tubercle. DIFFERENTIAL DIAGNOSIS Alcidedorbignya inopinata is similar in size to Harpyodus euros and H. decorus but it is much smaller than all the other Pantodonta. Alcidedorbignya inopinata differs from all the other Pantodonta in having single rooted P2 and p2, and a hook-like angular process of the dentary. Alcidedorbignya inopinata differs from all the other Pantodonta except Bemalambda in having a distinct (although short) neck of the astragalus. It further differs from Pantolambda bathmodon in the following characters: size approximately 60% (not 40% as stated by Muizon & Marshall 1992) smaller, lack of a mesostyle on the upper molars, broader stylar shelf, posteriorly protruding bilobate nuchal crest, a horse-shoe shaped ectotympanic (not expanded medially as in Pantolambda), more gracile limb bones, ulna distinctly bent anteriorly and medially, obtuse angle between the anterior edge of the radial and trochlear notches of the ulna (acute angle in Pantolambda), much less developed and less everted anteroventral iliac spine, medial condyle of the femur similar in size to the lateral one (i.e. not projecting posteriorly), presence of a well-developed interosseous crest on the medial edge of the fibula, presence of a distinct (although short) neck of the astragalus, cleft pedal ungual phalanges (In pantolambda the anterior pedal phalanges are cleft; the posterior are not), distal half of ungual phalanges deflected palmarly or plantarly. Alcidedorbignya inopinata further differs from Harpyodus decorus and H. euros in the well-separated paracone and metacone, the V-shaped centrocrista and the much thinner postcingulum, whereas in Harpyodus the cusps are connate at base, the postcingumlum is much thicker and the centrocrista is straight. Alcidedorbignya inopinata further differs from Bemalambda in the following characters: size approximately 75% smaller, well-separated paracone and metacone at base (not connate), lack of the anteroposterior compression of the upper molars, lack of the great enlargement of the metaconid observed in Bemalambda, much lower sagittal crest, bilobate nuchal crest, lack of a well-developed postorbital process, much lower sagittal crest, dorsoventrally lower dentary in its anterior half, condyloid process located well above the level of the occlusal plane of the molars, much longer neural process of the axis, presence of 13 thoracic, nine lumbar, and four sacral vertebrae (respectively 17T, 8L, and 3S in Bemalambda), more gracile limb bones, ulna distinctly bent anteriorly and medially, presence of a much less developed and everted anteroventral iliac spine, medial condyle of the femur similar in size to the lateral (i.e. not projecting posteriorly as in Bemalambda), and presence of a well-developed interosseous crest on the medial edge of the fibula. NB: some of the above-mentioned morphological differences between Alcidedorbignya and larger pantodonts may be related to allometric phenomenons, which yet remain to be investigated (e.g., robustness of limb bones)., Published as part of Muizon, Christian de, Billet, Guillaume, Argot, Christine, Ladevèze, Sandrine & Goussard, Florent, 2015, Alcidedorbignya inopinata, a basal pantodont (Placentalia, Mammalia) from the early Palaeocene of Bolivia: anatomy, phylogeny and palaeobiology, pp. 397-634 in Geodiversitas 37 (4) on pages 410-412, DOI: 10.5252/g2015n4a1, http://zenodo.org/record/5210632, {"references":["MUIZON C. DE & MARSHALL L. G. 1987 c - Le plus ancien Pantodonte (Mammalia) du Cretace superieur de Bolivie. Comptes Rendus hebdomadaires des Seances de l'Academie des Sciences, Paris 304: 205 - 208.","MUIZON C. DE & MARSHALL L. G. 1992. - Alcidedorbignya inopinata (Mammalia: Pantodonta) from the early Paleocene of Bolivia: phylogenetic and paleobiogeographic implications. Journal of Paleontology 66 (3): 499 - 520.","MARSHALL L. G., SEMPERE T. & BUTLER R. F. 1997. - Chronostratigraphy of the mammal-bearing Palaeocene of South America. Journal of South American Earth Sciences 10: 49 - 70.","LOFGREN D. L., LILLEGRAVEN J. A., CLEMENS W. A., GINGERICH P. D. & WILLIAMSON T. E. 2004. - Paleocene Biochronology: The Puercan through Clarkforkian Land Mammal Ages, in WOODBURNE M. O. (ed.), Late Cretaceous and Cenozoic Mammals of North America. Biostratigraphy and Geochronology. Columbia University Press, New York: 43 - 105.","WILSON G. P. 2013. - Mammals across the K / Pg boundary in Northeastern Montana, USA: Dental morphology and bodysize patterns reveal extinction selectivity and immigrant-fueled ecospace filling. Paleobiology 39: 429 - 469.","SPRAIN C. J., RENNE P. R., WILSON G. P. & CLEMENS W. A. 2014. - High-resolution chronostratigraphy of the terrestrial Cretaceous-Paleogene transition and recovery interval in the Hell Creek region, Montana. Geological Society of America Bulletin Published online on 16 September 2014. http: // dx. doi. org / 10.1130 / B 31076.1"]}

SALLATHERIUM REGUERO & CERDEÑO, 2005 SALLATHERIUM ALTIPLANENSE REGUERO & CERDEÑO, 2005 Below we describe a new specimen of S. altiplanense with slightly worn teeth which complements the original description. Diagnosis: Hegetotheriinae with nasals especially long and thin, not enlarged posteriorly. Labial groove on upper cheek teeth more medially placed than in Prohegetotherium. I1 enlarged, more oval in crosssection and more obliquely implanted than in Prohegetotherium, Hegetotherium and Hemihegetotherium. I2-I3-C more reduced than in Prohegetotherium and separated by diastemata, in contrast to Prohegetotherium and Hemihegetotherium, which have a closed dental series. P3-M3 with ovoid occlusal outline, different from the more quadrangular section of other hegetotheriines. Lower canine absent, i3 reduced, and a diastema separates i3 and p1. Lower p3 with anterior lobe longer than posterior lobe, in contrast to Prohegetotherium and Hemihegetotherium (Reguero & Cerdeño, 2005). Holotype: UF 91621, partial skull and associated incomplete mandible. Referred specimen: SAL 561, a right maxillary with P4-M3 (Fig. 23). Description SAL 561 represents a young adult as the teeth are very slightly worn and still present a pattern of fossettes. Referral of this material to S. altiplanense is difficult as young specimens of this species are not known so far. However, it presents cheek teeth that resemble hegetotheriids especially in their occlusal outline, which appear to be more regular than in Archaeohyrax. It also presents an M3 clearly smaller in surface area than M2 (Appendix S4, Table 5). These two characters are characteristic of hegetotheriids as compared with Archaeohyrax suniensis (see cladistic analysis) to which this specimen could have been referred in initial view (as they come from the same deposits and are of approximately the same size). Moreover, the coexistence of the fossettes is very different to that exhibited in Archaeohyrax suniensis, which represents the most distinct difference with this taxon. SAL 561 presents simultaneously an isolated central fossette on M1-3. This never occurs in A. suniensis. Besides the central fossette, an anterior– labial accessory fossette is present on M2-3. The co-occurrence of the central fossette and the labial accessory fossettes (here, only the anterior one) never occurs on Archaeohyrax and Protarchaeohyrax molars (Croft et al., 2003; see also Discussion of our cladistic analysis). If the assignment of this specimen to Sallatherium is correct, it demonstrates that the original pattern of hegetotheriid cheek teeth presents the typical face pattern of typotherians. Reguero & Cerdeño (2005: 680, fig. 6) referred to another hegetotheriid, Prohegetotherium schiaffinoi (Kraglievich, 1932), a specimen (MNHN-BOL-V 004152) from Salla with unworn upper cheek teeth. It also exhibits the co-occurrence of central and accessory fossettes. However, our re-examination of this specimen (quasi-unworn right P2-4) indicates that it is identical to unworn premolars of A. suniensis, a species to which it is referred here (Fig. 10). Patterson (1934b) described juvenile teeth of a hegetotheriid, the pachyrukhine Prosotherium, but they are very different from those of Sallatherium given that they never present the isolation of a central fossette., Published as part of Billet, Guillaume, Patterson, Bryan & Muizon, Christian De, 2009, Craniodental anatomy of late Oligocene archaeohyracids (Notoungulata, Mammalia) from Bolivia and Argentina and new phylogenetic hypotheses, pp. 458-509 in Zoological Journal of the Linnean Society 155 (2) on pages 482-483, DOI: 10.1111/j.1096-3642.2008.00445.x, http://zenodo.org/record/5444761, {"references":["Reguero MA, Cerdeno E. 2005. New late Oligocene Hegetotheriidae (Mammalia, Notoungulata) from Salla, Bolivia. Journal of Vertebrate Paleontology 25: 674 - 684.","Croft DA, Bond M, Flynn JJ, Reguero MA, Wyss AR. 2003. Large archaeohyracids (Typotheria, Notoungulata) from Central Chile and Patagonia, Including a Revision of Archaeotypotherium. Fieldiana Geology, N. S. 49: 1 - 38.","Patterson B. 1934 b. Upper premolar-molar structure in the Notoungulata with notes on taxonomy. Field Museum of Natural History, Geological Series 6: 91 - 111."]}

Billet, Guillaume, Muizon, Christian De, Quispe, Bernardino Mamani (2008): Late Oligocene mesotheriids (Mammalia, Notoungulata) from Salla and Lacayani (Bolivia): implications for basal mesotheriid phylogeny and distribution. Zoological Journal of the Linnean Society 152 (1): 153-200, DOI: 10.1111/j.1096-3642.2007.00388.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2007.00388.x

FAMILY ODOBENOCETOPSIDAE MUIZON, 1993 Type and only included genus: Odobenocetops Muizon, 1993. Diagnosis of the family: As for the type genus., Published as part of Muizon, Christian de & Domning, Daryl P., 2002, The anatomy of Odobenocetops (Delphinoidea, Mammalia), the walrus-like dolphin from the Pliocene of Peru and its palaeobiological implications, pp. 423-452 in Zoological Journal of the Linnean Society 134 (4) on page 424, DOI: 10.1046/j.1096-3642.2002.00015.x, http://zenodo.org/record/4687167

ODOBENOCETOPS LEPTODON MUIZON, DOMNING & PARRISH, 1999 (FIGS 1���12, TABLES 1 AND 2) Holotype: SMNK PAL 2492, an incomplete skull (lacking most of the dorsal and right sides of the braincase, right orbit, and right side of the right alveolar sheath), with the right ear bones and the atlas. Referred specimen: MNHN SAO 202, partial skeleton with partial skull lacking the right tusk and with the alveolar sheaths very damaged. Most of the braincase has been weathered away but the left periotic and a partial tympanic are preserved in situ. The postcranial skeleton is very poorly preserved, comprising only a few hyoid fragments, 26 partial vertebrae, several rib fragments, the distal half of the left humerus, most of the left radius, a proximal portion of the ulna lacking the olecranon, and fragments of carpals and metacarpals. MNHN PPI 249, a right periotic is referred to O. cf. leptodon . Etymology of the species name: from Greek: leptos (thin) and odon (tooth), in reference to the needle-like morphology of the large right tusk. Diagnosis: Odobenocetops leptodon differs from O. peruvianus in the morphology of the snout, which is more rounded and wider in dorsal view; in the lack of large premaxillary foramina; in the presence of small depressions for premaxillary sacs in the premaxillae, anterior to the bony nares; in the presence of supplementary rostral bones at the anterodorsal apex of the snout; in the broader, deeper, and longer palate; in the anterior border of the palate, which is more U-shaped, while it is more V-shaped in O. peruvianus; and in the straight (or slightly concave) anterodorsal border of the orbit, which is deeply concave in O. peruvianus. Locality, Horizon and Age: the holotype and MNHN SAO 202 are from the SAO level of the Pisco Formation in Peru (at approximately km 540 of the Panamerican Highway south of Lima). The SAO horizon has been defined by de Muizon & Bellon (1980) but see also de Muizon (1981), de Muizon & DeVries (1985), and de Muizon & Bellon (1986). Its age spans approximately from 4 to 3 Ma; therefore, the specimens are early Pliocene in age. The SAO level of the Pisco Formation is slightly younger than the SAS level (5���4 Ma), which yielded the holotype of O. peruvianus and the third specimen referred to here as a female of O. peruvianus. MNHN PPI 249, an isolated periotic, is from beds of the Pisco Formation located at c. 3 km east of Yauca (these beds may be slightly younger than those of the SAO horizon and may belong to the late Pliocene). Skull Basicondylar length: 415e Bizygomatic width: 150 �� 2 = 300e Minimum width of the skull posterior to the postorbital processes: 70 �� 2 = 140e Maximum width between the postorbital processes: 130 �� 2 = 260 Maximum width of both nares: 59e Maximum length of the left naris: 53.5e Width of the choanae: 104 Periotic Maximum width of the skull at the level of the exoccipitals: 123.5 �� 2 = 257e Anteroposterior length: 77.5e Maximum width (measured ventrally, approximately perpendicular to anteroposterior length: 42e Maximum width between the pterygoid crests: 142 Width between the apices of the hamular processes: 112 Length of pars cochlearis from contact with anterior process anteriorly to medial edge of aqueductus cochleae (measured dorsally): 29.5 Tympanic Length of the lateral lobe of the left tympanic: 54.2 Atlas Maximum width of the pars cochlearis in medial view: 30.8 Maximum width of the atlas: 174 Length of internal auditory meatus: 14.3 Maximum height of the atlas at sagittal plane: 106 Maximum vertical diameter of neural canal: 64.5 Maximum horizontal diameter of neural canal: 56.5 Limb Tympanic Length of the involucrum (measured medially): 58.8 Malleus Maximum length in posteromedial view (cf. Fig. 10A): 11.4 Maximum length of the radius: 117 Anteroposterior length of distal end of humerus: 60.1 Mediolateral width of distal end of humerus: 43 Maximum width in posteromedial view (cf. Fig. 10A): 6.05 DESCRIPTION The following description focuses on the differences between the two species of Odobenocetops. We refer to de Muizon et al. (2002) for the aspects of the cranial anatomy common to the two species. GENERAL FEATURES The general morphology of the skull of Odobenocetops leptodon is similar to that of O. peruvianus in its basic pattern (Figs 1���4). However, in dorsal view, the former differs from the latter in the morphology of the snout, which is much wider and more blunt. In anterior view the snout was more massive. Furthermore, if a melon was actually present, as hypothesized below, it is likely that the head of O. leptodon was more rounded than that of O. peruvianus. The skull of O. leptodon has the same bilobate outline as is observed in O. peruvianus, which is unique in a Neogene odontocete (de Muizon et al., 2002). This condition, where the frontals and maxillae do not overhang the temporal fossa, is found in primitive odontocetes such as Xenorophus, Agorophius and Archaeodelphis and in archaeocetes because of the lesser telescoping of the skull (Kellogg, 1936; Fordyce, 1981). In Odobenocetops it is regarded as a reversal of this typically cetacean telescoping. In general, the skull of O. leptodon is very heavily built and the bone is much denser, thicker, and more solid than in other delphinoids, being almost osteosclerotic in its posteroventrolateral angle. PREMAXILLA The premaxillae of O. leptodon are built on the same pattern as those of O. peruvianus (de Muizon et al., 2002). They both present a large alveolar process housing one tusk, the right tusk (of the presumed male, which is the only sex represented) being much larger than the left. Since the left alveolar process is not preserved on the holotype of O. peruvianus (the only specimen known when this species was first described) and because there are no other mammals which exhibit pronounced cranial asymmetry, it was hypothesized that the processes sheathing the tusks were both of the same size and that, consequently, the left tusk (which was judged to be shorter than the right sheath) was not erupted. The holotype of O. leptodon, however, indicates that the left sheath was clearly smaller than the right and that the left tusk was actually erupted. It is therefore probable that the condition of O. leptodon was also present in O. peruvianus. In the holotype of O. leptodon, the left sheath is transversely flattened and lies almost in a parasagittal plane (it diverges only slightly laterally). The right sheath is thicker because of the larger size of the tusk and diverges more markedly laterally. The region of the sheaths anterior to the tusks is strongly flattened and forms a posteriorly bent U-shaped lamina which borders the palate anteriorly. The anteroventral edge of this lamina is 0.5���1 cm thick, and presents longitudinal irregular ridges of bone to which was firmly attached the strong upper lip that was very probably present in O. leptodon as in O. peruvianus. The anterior and anterolateral side of each premaxillary sheath is a broad convex surface bearing several large grooves and foramina. These structures indicate an extensive vascularization of the anterior region of the skull, which is regarded here as related to the presence of a thick, muscular upper lip. In anterior view, in the sagittal plane, the snout is more elevated than in O. peruvianus and the surface of attachment of the upper lip is larger. Furthermore, the snout is wider in anterior view, and the anterior edge of the palate is grossly U-shaped rather than more Vshaped as in O. peruvianus. Therefore it is clear that the upper lip of O. leptodon was much larger than in O. peruvianus, indicating a larger vibrissal array and/or better suction ability in the former than in the latter. Dorsally, the morphology of the premaxillae of O. leptodon presents the major characters which differentiate this species from O. peruvianus. These bones are much wider than in O. peruvianus, and the right premaxilla is more expanded laterally because of the greater size of the tusk (Figs 2A and 3A). There are no enlarged premaxillary foramina as are observed in the other odontocetes, including O. peruvianus. This absence is regarded as a loss in O. leptodon which, in this respect, is more derived than O. peruvianus. The premaxillary foramina transmit branches of the internal maxillary artery and maxillary nerve from the infraorbital foramen (internal to the orbit) to parts of the nasofacial muscles anteriorly and posteriorly on the rostrum (see e.g. Schenkkan, 1973: fig. 5, on Mesoplodon bidens). In Odobenocetops these vessels and nerves are probably related to the irrigation and innervation of the strong upper lips and associated musculature as well as the possible vibrissae. In O. leptodon the canals conducting the nerves and vessels do not open dorsally but are clearly present. This is observed on the referred skull MNHN SAO 202 (Fig. 3A), in which the apex of the snout is eroded above the pulp cavity of the tusks. The canals passed above the proximal extremities of the tusks and apparently (clearly observable on the right side) divided into several smaller canals perforating the premaxillae to reach the upper lip anteriorly. Ramifications of the premaxillary canals are also observable on the lateral side of the premaxilla at the level of the antorbital notch, where several large foramina are present. It is likely that irrigation and innervation for the pulp cavities of the tusks were also transported by the premaxillary canals. The premaxillae of O. leptodon bear a small concave area, anterior to the bony nares, where lay the premaxillary sacs of the air sac system (Mead, 1975). These fossae for the premaxillary sacs are limited medially by the medial border of the premaxilla which overhangs the vomerian gutter; they are limited anteromedially by the suture with the rostral supplementary bone (see below); and anterolaterally they are medial to the posterior edge of each tusk alveolus (Figs 2A, 3A and 5). Fossae for premaxillary sacs are absent in O. peruvianus, where the space between the large premaxillary foramina and the anterior edge of the nares is so reduced that it was supposed that the premaxillary sacs were either very reduced or absent in this species (de Muizon et al., 2002). On the dorsal face of the skull the premaxillae of O. leptodon extend further posteriorly than in O. peruvianus. The posterior extremity of the left premaxilla is damaged on MNHN SAO 202, but it is clear that it lay slightly posterior to the posterior border of the nares. The posterior extremity of the right premaxilla lies about 5 cm posterior to the nares. On the holotype of O. peruvianus, the posterior extremity of the left premaxilla is located half-way between the anterior and posterior limits of the naris and on the right side (as well as on both sides of SMNK PAL 2491) it reaches the posterior edge of the naris. The Pmx-Mx suture is external to the nares, the border of which is formed by the maxillae only, in contrast to the condition of O. peruvianus in which the Pmx-Mx suture is internal to the nares in the anterior two-thirds of their length. In their dorsal portions the premaxillae of O. leptodon are relatively flat and not as salient as is observed in O. peruvianus. This feature is clearly observed on the lateral edges of the nares and at the level of the antorbital notch, where the premaxillae markedly overhang the maxillae in O. peruvianus, whereas the relief of these regions is much smoother in O. leptodon. The anterior sides of the premaxillae of O. leptodon (SMNK PAL 2492) bear strong foramina and grooves, which indicates an abundant vascularization related to the development of the upper lip. The premaxillae are much broader and much more elevated than in O. peruvianus, again indicating a larger and stronger upper lip (Figs 1B and 3C). The premaxillary sheaths, which house the tusks, are partly preserved on SMNK PAL 2492. The right is complete and the left is broken, apparently no more than 2 or 3 cm from the apex. Contrary to what was hypothesized in the case of O. peruvianus, the sheaths are not identical in size; the left one is clearly smaller and shorter than the right and reflects the size difference between the tusks. In lateral view, the right alveolar process forms an angle of c. 60�� with the dorsal plane of the skull (from the vertex to the anterodorsal tip of the rostrum). The anteroventral edges of the sheaths (which include the anterior edge of the palate) are thickened and corrugated, as is observed in O. peruvianus, which indicates attachments for strong, possibly horny, connective tissue for the attachment of the upper lip. This narrow edge also bears (in both species) a series of foramina, which could have been related to a fringe of vibrissae. In the style of feeding we have hypothesized, these could have allowed the animal to detect when the front edges of the sheaths were in contact with the sea floor. The anteroventral crest of the premaxillae (Figs 1B and 3C) has a very wide U-shape whereas it is more V-shaped in O. peruvianus. This morphology is the result of the widening of the snout and is possibly related to the presence of the supplementary bones described below. The U-shaped anterior border of the palate is not perpendicular to the sagittal plane. In other words, in anterior view, if the sagittal plane is positioned vertically (based on pterygoids, basioccipital and vomerian groove), the plane of the anterior crest of the palate dips towards the right side of the skull. This is because the anteroventral edge of the smaller and less laterally divergent left sheath is dorsal to (more elevated than) that of the right sheath. This condition implies that when the animal was feeding (i.e. with the anterior border of the palate parallel to the sea floor; see de Muizon, 1993b and de Muizon et al., 2002), the sagittal plane was inclined toward the left side of the animal (i.e. dipping toward the right side). Therefore, because of the asymmetry of the premaxillae, O. leptodon was feeding slightly inclined on left side. The premaxillae form the anterior region of the palate as is observed in O. peruvianus. Although the palate of O. leptodon is much broader than in O. peruvianus, the area occupied by the premaxillae in this part of the skull is only slightly larger than in O. peruvianus (see below). ROSTRAL BONES One of the most striking differentiating characters of O. leptodon is the presence of two supplementary bones (one on each side) anterior to the premaxillae at the anterodorsal apex of the snout. These bones are apparently appressed against the medial edges of the premaxillae and lie partly on the dorsal part of the skull and partly on the anterior slope of the snout. The dorsal portion is narrower than long but broadens anteriorly. It is limited posteriorly by the fossa for the premaxillary sac of the premaxilla, while medially it has a small contact with the medial portion of the maxilla on the dorsal face of the rostrum (Figs 1B, 2A, 3A and 5). Within the vomerian groove, the rostral supplementary bone is bordered by the medial portion of the maxilla, but the edge of the groove is formed by the rostral bone itself. The lateral suture is directed anteroposteriorly and is located just medial to the tusk alveoli. The anterior portion is not observable on MNHN SAO 202 but it is in relatively good condition on the left side of SMNK PAL 2492. It is also relatively narrow and forms a strip of bone overlying the premaxilla, tapering ventrally, and reaching (or almost reaching) the ventromedial border of the premaxilla at the anterior edge of the palate. Its medial suture is with the vomer. These supplementary bones are in fact wedged (as far as the dorsal portion is concerned) between the tusks laterally and the vomer and maxilla medially. They are partly responsible for the breadth of the snout in O. leptodon and tend to separate the proximal extremities of the tusks and alveoli (i.e. the premaxillae). As a probable consequence of their presence, the tusks are less divergent distally than in O. peruvianus and the anterior border of the palate is Ushaped in O. leptodon rather than more V-shaped as in O. peruvianus. Apparently, as is observed on the left premaxilla of SMNK PAL 2492, the rostral bones were anterodorsally protruding, forming an elevated prominence at the apex of the snout. This condition is not observable on MNHN SAO 202 since the bones have been partly eroded in their apical portions. These supplementary bones could be ossa prenasalia, cartilage bones which appear late in development (mainly in postnatal life) and which are not uncommon in mammals. They are paired or unpaired bones which articulate with the nasals or premaxillae and which are always related to the presence of a rhinarium (Rhynchocyon, Sus, Talpa, Chiroptera) or a proboscis (Starck, 1967). In the case of O. leptodon the supplementary bones present at the anterodorsal apex of the snout could be related to the thick and powerful upper lip used by Odobenocetops to forage on the bottom in search of food (de Muizon, 1993a;b; de Muizon et al., 2002). They could also indicate of the presence of a very sensitive tactile organ, with or without vibrissae (see de Muizon, 1993a), much more developed in O. leptodon than in O. peruvianus. It is likely that strong muscles for the upper lip of O. leptodon were attaching on the (?)prenasalia. However, it is noteworthy that the prenasalia of other mammals are generally not tightly articulated with the premaxillae and/or the nasals, and not distinctly paired. If these supplementary bones are not prenasalia, another alternative which could explain the condition of O. leptodon is the presence of septomaxillae. These bones are present in crossopterygians, lissamphibians, squamates, in all nonmammalian therapsids, and in all the nontherian mammals except multituberculates. The septomaxilla is absent in marsupials and placentals except in Xenarthra (Wible, 1990; Zeller et al., 1993). However, we are reluctant to interpret the supplementary bones of O. leptodon as septomaxillae, since the study of the development of the nasal capsule of odontocetes (Klima & Van Bree, 1985; Klima et al., 1986; Klima, 1987) does not show any indication that such bones are present at any developmental stage in this group. A third alternative is to regard the supplementary bones of O. leptodon as neomorphic elements different from prenasalia and septomaxillae, possibly related to the muscle attachment of the lip, which was probably much stronger than in O. peruvianus. TUSKS The tusks of O. leptodon are similar to those of O. peruvianus (Figs 1A,B). They are much better preserved in SMNH PAL 2492 than in the ho, Published as part of Muizon, Christian de & Domning, Daryl P., 2002, The anatomy of Odobenocetops (Delphinoidea, Mammalia), the walrus-like dolphin from the Pliocene of Peru and its palaeobiological implications, pp. 423-452 in Zoological Journal of the Linnean Society 134 (4) on pages 425-432, DOI: 10.1046/j.1096-3642.2002.00015.x, http://zenodo.org/record/4687167, {"references":["de Muizon C, Domning DP, Parrish M. 1999. Dimorphic tusks and adaptive strategies in a new species of walrus-like dolphin (Odobenocetopsidae) from the Pliocene of Peru. Comptes-rendus de l'Academie des Sciences, Paris, Sciences de la Terre et des Planetes 329: 449 - 455.","de Muizon C, Bellon H. 1980. L'age mio-pliocene de la Formation Pisco (Perou). Comptes Rendus de l'Academie des Sciences, ser. D 290: 1063 - 1066.","de Muizon C. 1981. Les vertebres fossiles de la formation Pisco (Perou). Premiere partie: Deux nouveaux Monachinae (Phocidae, Mammalia) du Pliocene de Sud-Sacaco. Travaux de l'Institut Francais d'Etudes Andines 22: 1 - 160.","de Muizon C, DeVries TJ. 1985. Geology and paleontology of late Cenozoic marine deposits in the Sacaco area (Peru). Geologisches Rundschau 74: 547 - 563.","de Muizon C, Bellon H. 1986. Nouvelles donnees sur l'age de la Formation Pisco (Perou). Comptes Rendus des Seances de l'Academie des Sciences, Ser. II (303): 1401 - 1404.","de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press.","Kellogg, AR. 1936. A review of the Archaeoceti. Carnegie Institute of Washington Publication 482: 1 - 366.","Fordyce RE. 1981. Systematics of the odontocete Agorophius pygmaeus and the family Agorophiidae (Mammalia: Cetacea). Journal of Paleontology 55: 1028 - 1045.","Schenkkan EJ. 1973. On the comparative anatomy and function of the nasal tracts in odontocetes (Mammalia, Cetacea). Bijdragen tot de Dierkunde 43: 127 - 159.","Mead JG. 1975. Anatomy of the external nasal passages and facial complex in the Delphinidae (Mammalia, Cetacea). Smithsonian Contributions to Zoology 207: 1 - 72.","de Muizon C. 1993 b. Odobenocetops peruvianus, una remarcable convergencia de adaptacion alimentaria. Bulletin de l'Institut Francais d'Etudes Andines 22: 671 - 683.","Starck D. 1967. Le crane des mammiferes. In: Grasse, PP, ed. Traite de Zoologie. Paris: Masson, 405 - 549.","de Muizon C. 1993 a. Walrus-like feeding adaptation in a new cetacean from the Pliocene of Peru. Nature 365: 745 - 748.","Wible JR. 1990. Petrosals of Late Cretaceous marsupials from North America, and a cladistic analysis of the petrosal in therian mammals. Journal of Vertebrate Paleontology 10: 183 - 205.","Zeller U, Wible JR, Elsner M. 1993. New ontogenetic evidence on the septomaxilla of Tamandua and Choloepus (Mammalia, Xenarthra), with a re-evaluation of the homology of the mammalian septomaxilla. Journal of Mammalian Evolution 1: 31 - 46.","Klima M, van Bree PJ. 1985. Uberzahlige Skeletelemente im Nasenschadel von Phocoena phocoena und die Entwicklung der Nasenregion bei den Zahnwalen. Gegenbaurs Morphologisches Jahrbuch 131: 131 - 178.","Klima M, Seel M, Deimer P. 1986. Die Entwicklung des hochspezialisierten Nasenschadels beim Pottwal (Physeter macrocephalus). Gegenbaurs Morphologisches Jahrbuch 132: 245 - 284.","Klima M. 1987. Morphogenesis of the nasal structures of the skull in toothed whales (Odontoceti). In: Kuhn H-J, Zeller U, eds. Morphogenesis of the Mammalian Skull. Mammalia Depicta 13: 105 - 121.","Hay KA, Mansfield AW. 1989. Narwhal, Monodon monoceros Linnaeus, 1758. In: Ridgway, SH, Harrison R, eds. Handbook of Marine Mammals, Vol. 4: River Dolphins and the Larger Toothed Whales. London: Academic Press, 145 - 176.","Porsild MP. 1922. Scattered observations on narwhals. Journal of Mammalogy 3: 8 - 13.","Miller ME, Christensen GC, Evans HE. 1964. Anatomy of the dog. Philadelphia: W. B. Saunders."]}

Muizon, Christian de, Domning, Daryl P. (2002): The anatomy of Odobenocetops (Delphinoidea, Mammalia), the walrus-like dolphin from the Pliocene of Peru and its palaeobiological implications. Zoological Journal of the Linnean Society 134 (4): 423-452, DOI: 10.1046/j.1096-3642.2002.00015.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1046/j.1096-3642.2002.00015.x

ODOBENOCETOPS PERUVIANUS MUIZON 1993 (FIGURES 13���15, TABLE 3) A second skull of Odobenocetops peruvianus has been discovered in the earliest Pliocene beds of the Pisco Formation at Sud-Sacaco. This specimen is of special interest because it is more complete than the holotype and especially because it bears two small tusks similar in size to the small tusk of the holotype (USNM 488252) and has therefore been regarded as a female of O. peruvianus (de Muizon et al., 1999). In the following discussion, we do not exhaustively describe the new skull, but simply describe the new features O. peruvianus provided by the new specimen. Holotype: USNM 488252, an incomplete skull lacking much of the left side and all of the auditory bones. Referred specimens: SMNK PAL 2491, a relatively complete skull which lacks only the posterodorsal roof of the braincase, and which still retains the ear bones in situ; MNHN SAS 1613, a left periotic and partial tympanic; and MNHN SAS 1614, a left periotic. Emended diagnosis: Odobenocetops peruvianus differs from O. leptodon in its snout, which is narrower at its apex and tapers dorsally (although the apex is still rounded); in the presence of large premaxillary foramina, anterior to the nares; in the absence of depressions for premaxillary sacs; in the shorter and shallower palate (especially in the anterior region); in the anterior border of the palate which is more Vshaped whereas it is more U-shaped in O. leptodon; and in the deeply notched anterodorsal edge of the orbit, which is slightly concave in O. leptodon. DESCRIPTION TUSKS AND PREMAXILLAE The major differences between the new specimen and the holotype are in the size of the tusks and morphology of the premaxillae. Both tusks are small and the left tusk is slightly smaller in diameter than the right. Neither of the tusks is complete. The left tusk is broken inside the sheath; however, the right tusk is only lacking its apex and, as preserved, is 23 cm long and is probably missing a few cm only. Therefore, the right tusk was very close to the length as well as the diameter of the small left tusk of O. leptodon. Although the tusk is not complete, given the length of the tusk (as preserved) and the sheath, it is certain that it was erupted. The premaxillary sheaths are small, and, in agreement with the sizes of the tusks, the left one is smaller than the right. Because of this slight asymmetry and although the apices of the left sheath and tusk are not preserved, it is likely that the left tusk was also erupted. Furthermore, the walls of the left sheath at its apex are very thin, which suggests that very little of the bone is missing. The apex of the right sheath is not completely preserved either, but given the thickness of the bone at the broken extremity, it is probable that no more than a few centimeters are lacking. Basicondylar length: 412 Bizygomatic width: 158 �� 2 = 316e Minimum width of the skull posterior to the postorbital processes: 116 The dorsal aspect of the premaxillae is very similar to that of the holotype although slightly more symmetrical. The posterior extension of the right prem axilla behind the nares is only slightly greater than that of the left, contrary to the condition of the holotype, in which the posterolateral process of the left premaxilla reaches the middle of the lateral edge of the left naris, whereas the right process almost reaches the posterior edge of the right naris. Since the premaxillae of SMNK PAL 2491 project posteriorly slightly behind the bony naris, this feature shows some variation within the species. The asymmetry of the tusks and alveolar processes may thus be reflected in the asymmetry of the posterior processes of the premaxillae. However, this inference must be made cautiously since most odontocetes (including monodontids) present an asymmetry of the dorsal bones of the skull, the right premaxilla and maxilla extending farther posteriorly than the left and slightly displacing the vertex on the left side of the skull. Nevertheless, the asymmetry of the male narwhal does not reflect the tusk asymmetry since the right maxilla is slightly more expanded posteriorly than the left, which carries the large tusk. Minimum width between the dorsal edges of the orbits: 123 Maximum width between the postorbital processes: 226 Width of the snout between the antorbital notches: 87 Maximum width of both nares: 60 Maximum length of the right naris: 51.5 Width of the choanae: 96 Maximum width of the skull at the level of the exoccipitals: 250 Bicondylar width: 143 Width between the apices of the hamular processes: 128 Length of the lateral lobe of the left tympanic: 48.5 In SMNK PAL 2491 the snout is very complete and the structure of the bone is perfectly preserved. Therefore, muscle scars and foramina are clearly observable and provide important data. Anterior to the large premaxillary foramina is a rough, triangular surface, distinct on each bone, which reaches the apex of the snout. This area corresponds to the attachment scar for the nasal plug muscle in the other odontocetes. These muscle scars are so well marked that it is unlikely that there was no nasal plug muscle in O. peruvianus. It is therefore very probable that O. peruvianus had nasal plugs, which is to be expected in an odontocete, but was not clear on the holotype (de Muizon et al., 2002). Posterior to the premaxillary foramina are two short saddle-shaped grooves, which form the anterior edges of the bony nares. The morphology of the new specimen confirms the conclusions of de Muizon et al. (2002) that, if premaxillary sacs (which are located between the premaxillary foramina and the anterior edge of the nares) were present in Odobenocetops peruvianus, they were very reduced, probably vestigial. Therefore, and considering the reduced space on the dorsal face of the rostrum, it is highly probable that O. peruvianus had no (or only a vestigial) melon. Although the nasal plugs, premaxillary sacs and melon are tightly related organs, the well-developed muscle scars for the insertion of the nasal plug muscle force us to conclude that O. peruvianus exhibited a strong reduction of the two latter organs but little reduction of the former. On the anterior face of the snout the premaxillae bear several large foramina indicative of an extensive vascularization of the snout related to the inferred presence of a large and strong upper lip. The irregular surface of the bone in this region corresponds to the attachment of a very robust musculature of the lip. The morphology of the much better preserved female specimen of O. peruvianus (SMNK PAL 2491) confirms the hypotheses based on the holotype of the species. MAXILLAE AND FRONTALS Posterior to the nares, between the mesethmoid and the maxillae, are two small triangular medial portions of the frontals, which have the same condition as the maxillae in relation to the premaxillae at the anterior region of the nares. In other words, the maxillae, which lay on the frontals, have withdrawn posterior to the nares, uncovering the frontals. Posteriorly, the medial portions of the frontals become thin and progressively disappear after the maxillae become joined. Further posteriorly, the medial edges of the maxillae separate again and uncover a thin strip of the frontals which widens posteriorly. On the holotype it is probable that the lower portion of the mesethmoid posterior to (and overhung by) the Y-shaped portion which separates the nares (see de Muizon et al., 2002) is in fact the medial portion of the frontal observed on the female skull fused to the mesethmoid. A medial portion of the frontal is clearly present in O. leptodon (MNHN SAO 202). The extensions of the maxillae posterior to the nares narrow posteriorly but are, like the premaxillae and tusks, relatively symmetrical, whereas in the male the right maxilla is wider and extends further posteriorly than the left. The preorbital process of the frontal of the female skull is anteriorly elongated and blade-like, as in the holotype. However, in this specimen it is clear that both the maxilla medially and the frontal laterally are components of the process. Therefore, although highly modified, the preorbital process of O. peruvianus resembles that of the other odontocetes in the combined participation of the maxilla and frontal. The postorbital process is similar in shape to that of the holotype but is larger and longer, indicating some individual variation of this character. A clear asymmetry of the frontal is present, as is observed in the other odontocetes, in which the right supraorbital process of the frontal is distinctly larger than the left. PALATINE, PTERYGOID AND VOMER The vomer is very wide, the maxillae do not participate in the construction of the palate, and the premaxillae and the palatines have a large V-shaped suture on both sides as is observed in the holotype. The posterior region of the palate is perfectly preserved and adds to the knowledge of the species. In the posterior region of the palate, the medial edges of the palatines are in contact, hiding the vomer for a few centimetres of its length. Further posteriorly the palatines separate again, uncovering the vomer ventrally. The median ridge of the vomer projects about 7 cm posterior to the posterior edges of the palatines. The sutures with the pterygoids are widely separated. The apices of the pterygoid hamuli are sharply pointed and extend toward the anterior angle of the basioccipital crests formed by the medial laminae of the pterygoids. They are almost in contact on the right side and the anterior end of the left medial lamina is apparently broken. Because of this projection and the long nonpalatal ridge of the vomer, the palate of O. peruvianus is clearly shorter than in O. leptodon and its posterior border is strongly concave. The pterygoid hamulus is transversely compressed and the lateral lamina of the pterygoid almost contacts the medial lamina. Therefore, the fossa for the pterygoid sinus is extremely reduced (as observed by de Muizon et al., 2002 on the holotype) and hardly present in O. peruvianus. It is clearly more reduced than in O. leptodon, in which the fossa is very small but conspicuous. As in O. leptodon, there is a short but continuous lateral lamina of the pterygoid, which contacts the alisphenoid, contrary to the condition in Recent delphinoids. However, in Recent monodontids, a continuous lateral lamina of the pterygoid, although almost absent from the pterygoid hamulus, is sometimes present and contacts the squamosal dorsally. ALISPHENOID The alisphenoid is similar to that of O. leptodon. It is very thick and bears an enormous foramen ovale not confluent with the cranial hiatus. de Muizon et al. (2002) stated that in the holotype of O. peruvianus the foramen ovale was confluent with the cranial hiatus. Because this is not the case in the three other skulls referred to Odobenocetops, it is possible that the condition observed in the holotype is due to a postmortem breakage of the alisphenoid. As in O. leptodon the external opening of the foramen ovale is formed anteriorly by the pterygoid and posteriorly by the alisphenoid. Internally, the foramen ovale is fully enclosed in the alisphenoid. It is noteworthy, however, that this condition is not easy to observe because of the partial fusion of the bones. SQUAMOSAL AND EAR BONES The squamosal of SMNK PAL 2491 is basically similar to that of the holotype. The tympanic and the periotic are preserved in situ on both sides of the specimen (Fig. 15). Since the bones could not be removed from the skull it is not possible to describe them thoroughly. However, it is clear that they are extremely similar to those referred to the species by de Muizon et al. (2002). The lateral face of the tympanic bears a large sigmoid process which is grossly perpendicular to the anteroposterior axis of the bone and not shifted posteriorly as in the classical (i.e. non-odobenocetopsid) delphinoids. The apex of the process is straight, rounded, and not strongly recurved anteriorly as is observed in the classical delphinoids. Posterior to it is a low conical process and a relatively large anterior border of the posterior process. These three elements surround the external auditory meatus and, as a consequence of their morphology, the meatus is much larger than in the classical delphinoids. It is slightly smaller than in O. leptodon (SMNK PAL 2492). This condition would indicate a more efficient (effective) tympanic membrane in the Odobenocetopsidae and therefore possibly better sound perception via the middle ear than in the other odontocetes. The lateral wall of the tympanic is high, as is observed in O. leptodon. This condition indicates that the middle ear cavity was larger than in the classical delphinoids. It resembles the condition of most early diverging odontocetes (Squalodontidae, Squalodelphinidae, Platanistidae, Eurhinodelphinidae), and could represent a plesiomorphic condition or, more likely, a reversal corresponding to a need for enlargement of the middle ear cavity. The anterior extremity of the tympanic is blunt and rounded, as is observed in the other delphinoids. The ventral lobes are well separated by a deep median groove which is well-marked on the posterior two-thirds of the bone. Their posterior extremities are rounded and wide and the medial lobe is slightly posterior to the lateral. This condition is similar to that of O. leptodon but clearly differs from that of the Recent monodontids, in which the posterior extremity of the medial lobe is narrower and more anterior than that of the lateral lobe. This feature is especially obvious in Monodon. It is also present to a lesser extent in the delphinids and phocoenids. Again, the odobenocetopsid condition is found in the early diverging odontocetes mentioned above, but is regarded here as a reversal (rather than a plesiomorphy). Not much can be said about the periotic, which is preserved in situ, except that it has the massive morphology observed on the referred specimens described by de Muizon et al. (2002). Contrary to what is observed in the classical delphinoids, the lateral portion of the bone is closely appressed against the squamosal, in this respect resembling the condition observed in the platanistoids (sensu de Muizon, 1987; 1991; 1994; Fordyce & Barnes, 1994; Fordyce et al., 1994; Fordyce, 1994; not sensu McKenna & Bell, 1997). Furthermore, the posterior process of the periotic is deeply wedged between the squamosal and the exoccipital, which is in agreement with the long posterior process observed on MNHN SAS 1614 (an isolated periotic from the same horizon as the holotype of O. peruvianus and referred to this species). A similar condition is present in Delphinapterus (Kasuya, 1973) and Monodon. The delphinids and phocoenids are characterized by a petrotympanic completely isolated from the skull and maintained in situ by ligaments only (Fraser & Purves, 1960). Early derived odontocetes such as platanistoids have a tympanic and a periotic still articulated with the squamosal, which is regarded as a plesiomophic character state (de Muizon, 1987; 1991; 1994). Therefore, the condition of Odobenocetops and the Monodontidae could be regarded as plesiomorphic. However, because they have synapomorphies of the Delphinoidea absent in the Platanistoidea, we rather consider the condition of Odobenocetops as a reversal due to its hyperspecialization. The fact that a condition approaching this one is also found in monodontids could represent a synapomorphy of the two families, possibly related to sound transmission. In general, the periotic and tympanic of Odobenocetops have relatively tight and extensive contacts with the surrounding bones: basioccipital and squamosal for the tympanic, and squamosal and exoccipital for the periotic. The lateral tuberosity and rim of the anterior process of the periotic are closely appressed against the squamosal in a similar pattern to that observed in the platanistoids. The squamosal in this region is greatly thickened and forms the medial border of the trough-like glenoid cavity. On the anterior region of the anterior process of the periotic are several independent bony nodules which are appressed against the anterior process and apparently part of it. Such a condition has been observed in O. leptodon and is also present sometimes in Platanista. BASIOCCIPITAL The basioccipital is extremely wide and basically similar to that of O. leptodon although slightly wider. The basioccipital crests are large and undergird the tympanics, which are partially imbedded in their lateral face. The posteromedial faces of the basioccipital crests bear very large and deep muscular scars for insertion of the scalenus, at least as strong as in O. leptodon. EXOCCIPITAL The paroccipital process is very large and stout. It differs from that of the holotype in being orientated ventrally and not ventrolaterally. Its ventromedial angle contacts the posteroventral angle of the basioccipital crest and encloses the jugular notch to form a relatively large window, as is observed in O. leptodon. The exoccipital border of the window is very thick and forms an elevated crest. This indicates a strong scalenus dorsalis, which is inserted on the posteroventral face of the paroccipital process. This part of the occipital indicates an exceptionally strong musculature of the neck as was noted in regard to the holotype of Odobenocetops peruvianus (de Muizon et al., 2002). The anterior face of the paroccipital process does not present any fossa for the posterior sinus such as is observed in many other delphinoids. Fraser & Purves (1960) have stated that the absence of a fossa is not equivalent to absence of a posterior sinus. As a matter of fact, in the Recent monodontids the anterior face of the paroccipital process is not excavated by a fossa and a small posterior sinus is present. However, the presence of a large sinus is related to a deep fossa. In SMNK PAL 2491 the anterior face of the paroccipital process has a reduced area and is not indicative of a large posterior sinus. This statement contrasts with the observations made on the holotype of O. peruvianus (de Muizon et al., 2002). The occipital condyles are more convex and salient than in any recent delphinoid and confirm the great mobility of the neck which was noted with regard to the holotype. In fact, the occipital condyles form a quarter of a sphere (Figs 13B,D and 14) and are proportionally larger and more convex than in any other cetacean (Recent or fossil) or in the walrus. The morphology of the condyles of SMNK PAL 2491 therefore indicates an exceptional mobility of the neck in Odobenocetops; certainly much greater than that of any other odontocete., Published as part of Muizon, Christian de & Domning, Daryl P., 2002, The anatomy of Odobenocetops (Delphinoidea, Mammalia), the walrus-like dolphin from the Pliocene of Peru and its palaeobiological implications, pp. 423-452 in Zoological Journal of the Linnean Society 134 (4) on pages 439-444, DOI: 10.1046/j.1096-3642.2002.00015.x, http://zenodo.org/record/4687167, {"references":["de Muizon C, Domning DP, Parrish M. 1999. Dimorphic tusks and adaptive strategies in a new species of walrus-like dolphin (Odobenocetopsidae) from the Pliocene of Peru. Comptes-rendus de l'Academie des Sciences, Paris, Sciences de la Terre et des Planetes 329: 449 - 455.","de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press.","de Muizon C. 1987. The affinities of Notocetus vanbenedeni, an early Miocene platanistoid (Cetacea, Mammalia) from Patagonia, southern Argentina. American Museum Novitates 2904: 1 - 27.","de Muizon C. 1991. A new ziphiid (Odontoceti, Mammalia) from the Early Miocene of Washington state (USA) and a phylogenetical analysis of the major groups of odontocetes. Bulletin du Museum national d'Histoire naturelle, 4 e ser., Sect. C 12: 279 - 326.","de Muizon C. 1994. Are the squalodonts related to the platanistoids? In: Berta A, Demere TA, eds. Contributions in Marine Mammalogy Honoring Frank C. Whitmore Jr. Proceedings of the San Diego Society of Natural History 29: 135 - 146.","McKenna MC, Bell SK. 1997. Classification of Mammals Above the Species Level. New York: Columbia University Press.","Kasuya T. 1973. Systematic consideration of Recent toothed whales based on the morphology of the tympano-periotic bone. Scientific Reports of the Whales Research Institute 25: 1 - 103.","Fraser FC, Purves PE. 1960. Hearing in cetaceans: evolution of the accessory air sacs and the structure and function of the outer and middle ear in recent cetaceans. Bulletin of the British Museum of Natural History (Zoology) 7: 1 - 140."]}

Bouetel, Virginie, Muizon, Christian de (2006): The anatomy and relationships of Piscobalaena nana (Cetacea, Mysticeti), a Cetotheriidae s.s. from the early Pliocene of Peru. Geodiversitas 28 (2): 319-395, DOI: http://doi.org/10.5281/zenodo.5376036

Bouetel, Virginie, Muizon, Christian de (2006): The anatomy and relationships of Piscobalaena nana (Cetacea, Mysticeti), a Cetotheriidae s.s. from the early Pliocene of Peru. Geodiversitas 28 (2): 319-395, DOI: http://doi.org/10.5281/zenodo.5376036, {"references":["BARNES L. G. & MCLEOD S. A. 1984. - The fossil record 1984, 1988; Barnes 1985a, b). According to this, and phyletic relationships of gray whales, in JONES it seems that the Cetotheriidae s.s. have a relatively M. L., SWARTZ S. L. & LEATHERWOOD S. (eds), The wide paleogeographic distribution, although mainly Gray Whale: Eschrichtius robustus. Academic Press, located in the northern hemisphere. Orlando: 3-32.","H. 1994. - Classification and distribution of the","Oligocene Aetiocetidae (Mammalia; Cetacea; Mys- Acknowledgements ticeti) from western North America and Japan. The Special thanks are due to R. E. Fordyce (University Island Arc 3: 392-431. of Otago, Dunedin, New Zealand) and anony- BENHAM W. B. 1937. - Fossil Cetacea of New Zealand. mous reviewer for their very careful work, which II. On Lophocephalus, a new genus of zeuglodont","Cetacea. Transactions of the Royal Society of New greatly helped in improving the initial version of Zealand 67: 1-7. this work. Specimens were collected by CM with BENHAM W. B. 1939. - Mauicetus: a fossil whale. funds of the Institut francais d'Etudes andines Nature 143: 765. (IFEA) and of the Museum national d'Histoire BENHAM W. B. 1942. - Fossil Cetacea of New Zeanaturelle (MNHN). The \"Societe des Amis du land. V. Mauicetus, a generic name substituted for","Lophocetus Benham. Transactions of the Royal Society Museum national d'Histoire naturelle et du Jar- of New Zealand 71: 260-270. din des Plantes\" provided financial support to BOUETEL V. 2005. - Phylogenetic implications of VB for two short term visits to the USNM and skull structure and feeding behavior in balaenopto the LACM. E. Frey (Staatlische Museum fur terids (Cetacea, Mysticeti). Journal of Mammalogy Naturkunde, Karlsruhe, Germany) gave CM access 86 (1): 139-146.","BRANDT J. F. 1843. - De Cetotherio, novo balaenarum to the holotype of Piscobalaena nana and provided, familiae genere, in Rossia meridionali anti aliquot anas usual, an extremely helpful and kind attention. nos effoso. Bulletin de l'Academie imperiale des Sciences M. Elstrup kindly provided original photographs de St Petersbourg (2) 1: 145-148. of the holotypes of Cetotherium rathkei and Metopo- BRANDT J. F. 1872. - Bericht uber den bereits vollencetus durinasus. Thanks are due also to L. G. Barnes deten, druckfertigen Theil seiner Untersuchungen uber die fossilen und subfossilen Cetaceen Europas. (LA county Museum), D. Bohaska (Department Compte rendu de l'Academie imperiale des Sciences de of Paleobiology, USNM), J. G. Mead and C. W. St Petersbourg tome 17: 407-408. Potter (Marine Mammal Program, USNM), who BRANDT J. F. 1873. - Untersuchungen uber die fosprovided VB access to the specimens of fossil and silen und subfossilen Cetaceen Europas. Memoires de Recent mysticetes under their care. Photographs l'Academie de St Petersbourg 20 (1), ser. 7: 1-371.","CABRERA A. 1926. - Cetaceos fosiles del Museo de la are by P. Loubry and D. Serrette (MNHN); line Plata. Revista del Museo de la Plata 29: 363-411. drawings are by VB except Figure 10, which is by CAPELLINI G. 1901. - Balenottera miocenica del monte F. Pilard. titano, Republica di S. Marino. Memorie della reale","COPE E. D. 1896. - Sixth contribution to the knowledge GEISLER J. H. & SANDERS A. E. 2003. - Morphologiof the Miocene fauna of North Carolina. Proceed- cal evidence for the phylogeny of Cetacea. Journal of ings of the American Philosophical Society 35 (151): Mammalian Evolution 10: 23-129.","139-146. HASEGAWA Y., NOKARIYA H., SATO J. & OISHI M. CUMMINGS W. C. 1985. - The right whales Eubalae- 1985. - Part III. 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Bulletin of the Research Bulletin 32: 5-17.","Museum of Natural History, University of Oregon ICHISCHIMA H. 1997. - Systematics of the Latest Oligocene 3: 1-51. to the Earliest Miocene Mysticeti from New Zealand. FORDYCE R. E. 1980. - Whale evolution and Oligocene Dissertation, University of Otago, Dunedin, New Southern Ocean environments. Palaeogeography Pal- Zealand, xx + 352 p.","aeoclimatology Palaeoecology 55: 319-336. KELLOGG R. 1924. - Description of a new genus and FORDYCE R. E. 1989. - Origins and evolution of Ant- species of whalebone whale from the Calvert Cliffs arctic marine mammals. Special Publication of the Maryland. Proceedings of the United States National Geological Society of London 47: 269-281. Museum 63: 1-14.","FORDYCE R. E. 1992. - Mauicetus and late Oligocene KELLOGG A. R. 1928. - History of whales - their adapbaleen-bearing primitive Mysticeti from the South- tation to life in the water. Quarterly Review of Biology west Pacific, in Abstracts, 29th International Geological 3: 29-76, 174-208.","Congress, Kyoto, Japan 2: 349. KELLOGG R. 1929. - A new cetothere from south- FORDYCE R. E. 1994. - Waipatia maerewhenua, new ern California. University of California Publications, genus and new species (Waipatiidae, new family), an Bulletin of the Department of Geological Sciences 18: archaic late Oligocene dolphin (Cetacea: Odontoceti: 449-457.","Platanistoidea) from New Zealand. Proceedings of the KELLOGG R. 1931. - Pelagic mammals from the Tem- San Diego Museum of Natural History 29: 147-176. blor formation of the Kern River region, California. FORDYCE R. E. & MUIZON C.DE 2001. - Evolutionary Proceedings of the Californian Academy of Science series history of cetaceans: a review, in MAZIN J. M. & BUF- 4, 19: 217-297.","FRENIL V. DE (eds), Secondary Adaptation of Tetrapods KELLOGG R. 1934. - The patagonian fossil whalebone to Life in Water. Pfeil Verlag, Munich: 169-233. whale Cetotherium moreni (Lydekker). Carnegie Insti- FORDYCE R. E. & WATSON A. G. 1998. - Vertebral tution of Washington Publication 447: 64-81."]}