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Postprint of the manuscript published in Swiss Journal of Palaeontology: Maridet, O., Wu, W.-Y., Ye, J., Ni, X.-J., Meng, J., 2011. New discoveries of glirids and eomyids (Mammalia, Rodentia) in the Early Miocene of the Junggar basin (Northern Xinjiang province, China). Swiss Journal of Palaeontology130, 315–323. https://doi.org/10.1007/s13358-011-0022-7

Gomphos shevyrevae, new species HOLOTYPE: A right M1 (IVPP V 14669). PARATYPE: A right m1 (IVPP V 14670). INCLUDED SPECIMENS: A right P4 (or P3) (V14671.1), a right M1 (V14671.2), a right M2 (V14671.3), a left M2 (V14671.4), a right m1 (V14672.1), a right m2 (V14672.2), a left m3 (V14672.3), a left calcaneus (V14673), and a left astragalus (V14674). ETYMOLOGY: The species name is in honor of N.S. Shevyreva who named Gomphos elkema. DIAGNOSIS: Differs from Gomphos elkema and G. ellae in having more robust teeth with higher crowns, inflated cusps; upper molars with more posteriorly expanded hypocone and shelf; absence of the ridge connecting the lingual and labial cusps on P4; lower molars with relatively long trigonid and short talonid, reduced mesoconid and hypoconulid, and absence of the mesostylid; further differs from G. elkema in having extra facets on the calcaneus for articulation with the astragalus and navicular (unknown for G. ellae). TYPE LOCALITY AND AGE: Huheboerhe escarpment, Erlian Basin of Nei-Mongol, Middle Eocene lower beds of the Irdin Manha Formation. COMPARATIVE DESCRIPTION: Measurements of all teeth are in table 1. The tooth we identified as a P4 could also be a P3 (fig. 2). However, the anterior border of P3 is usually narrower than the posterior border in Gomphos. This tooth has its anterior portion TABLE 1 Tooth measurements of Gomphos shevyrevae (in mm) as wide as the posterior and bears a tiny posterolingual cusp, suggesting that it is likely a right P4. The P4 is a recently erupted tooth that bears no wear. As is typical of Gomphos, the P4 is unilaterally hypsodont and consists of a lingual main cusp, presumably the protocone, and a labial cusp. The lingual cusp is crescent shaped, and its two lophs form the anterior and posterior edges of the tooth. The labial cusp is conical, having a steeper labial surface and a more rounded lingual surface. Unlike P4 of Gomphos elkema, in which P4 is known (Meng et al., 2004; Asher et al., 2005), the ridge connecting the two cusps is absent in G. shevyrevae; instead, there is a weak ridge extending from the labial cusp anterolingually to join the midpoint of the anterior loph. The absence of a connection between the lingual and labial cusps of P4 recalls the condition found in Mimotona (Li, 1977; Li and Ting, 1993). Upper molars have one major lingual and two minor labial roots. The enamel is thick. M1 is so assigned because its hypocone and shelf are less expanded posteriorly than those of M2, and M1 is usually proportionally shorter than M2 (fig. 2). M1 of G. shevyrevae is similar to that of G. elkema in general morphology. However, the M1 and other upper cheek teeth of G. shevyrevae are more robust with more inflated cusps and stronger lophs. The protocone and its anterior and posterior lophs form a V-shaped structure with a slightly rounded apex (the lingual side of the protocone). The angle created by the lophs is about 45 ��. The lingual portion of the anterior loph may be homologized with the preprotocrista and the labial portion, which is much thinner, with the preparaconule crista. A paraconule (protoconule) is not distinct, but is indicated by a slight inflation where the postparaconule crista joins the anterior loph. Absence of the paraconule is common in basal Glires, both in simplicidentates, such as Matutinia and Rhombomylus (Ting et al., 2002; Meng et al., 2003), and duplicidentates, such as Mimotona and Gomphos (Li, 1977; Li and Ting, 1993; Meng et al., 2004), but it is usually present in taxa that are more closely related to rodents and in basal rodents, such as Tribosphenomys (Meng et al., 1994, 2007b; Meng and Wyss, 2001), Neimengomys (Meng et al., 2007b), Archetypomys (Meng et al., 2007a), and Cocomys (Li et al., 1989). There is a weak ridge between the paracone and the anterior loph, which is probably the postparaconule crista. The metacone is small- er and more lingually positioned than the paracone. It is connected with the protocone by the posterior loph of the protocone. The latter loph is strong, almost as wide as the metacone. A mesostyle occurs at the posterior base of the paracone, which blocks the labial exit of the narrow trigon basin. The metaconule is present, but is difficult to distinguish in heavily worn specimens. In lightly worn specimens (fig. 2E) a broader wear facet indicates the metaconule that must be higher and broader than the crista in order for such a wear pattern to be created. In G. elkema the posterior loph of the protocone is relatively slimmer and there is usually a restriction labial to the protocone. The hypocone and the postcingulum are well developed, and both structures are expanded posteriorly. The hypocone is separated from the protocone by a transverse groove, and a similar condition occurs on M2. This condition appears to differ from the morphology prevailing in G. elkema and G. ellae. In well-worn specimens (fig. 2C), however, the protocone and hypocone become confluent. On the lingual surface of the tooth, a vertical groove between the protocone and hypocone exists near the occlusal surface of the tooth, and this feature also seems more pronounced than on upper molars of G. elkema and G. ellae. M2 is similar to M 1 in general morphology, but it is proportionally longer. The mesostyle is reduced, either being incorporated into the posterior base of the paracone or entirely absent. No M3 was collected. The lower molars have an anterior and a posterior root. The tooth crown is somewhat higher than that of G. elkema and G. ellae. As in the upper molars, the enamel appears thicker than that of G. elkema and G. ellae. The m1 is identified as such because it has a transversely oriented, ridgelike hypoconulid (fig 3). In Gomphos, the lower molar hypoconulid becomes more pronounced posteriorly. The m1 and m2 are very similar except that m2 has a more posteriorly projecting hypoconulid. The lower molars are proportionally wider, and therefore relatively shorter, than those of other species of the genus. Lower molar trigonids are proportionally longer in relation to their corresponding talonid than is the case in other species of the genus. As is typical of Gomphos, the protoconid and metaconid are transversely aligned, and the trigonid has nearly vertical anterior and posterior walls. The protoconid and the metaconid are subequal in size. The protoconid is worn more extensively and is therefore lower than the metaconid. The protoconid sends the paralophid (paracristid) to the anterolingual base of the metaconid and the protolophid (protocristid) to the posterior base of the metaconid. A crescentic trigonid basin is enclosed by the trigonid cusps and lophids. Lower molar talonids are as wide as the trigonid and are longer than their corresponding trigonid. The hypoconid is as large as the protoconid and is very close to the posterior wall of the trigonid, so that the hypoflexid becomes a narrow groove. The cristid obliqua (ectolophid) is short and the mesoconid appears very weak relative to other mimotonids. The entoconid is low. Unlike the condition in G. elkema and G. ellae, in which a mesostylid is present (Meng et al., 2004; Kraatz et al., 2009), the mesostylid is absent in the new species. Because of the reduction of the mesoconid and cristid obliqua, the talonid basin is a broad, featureless concavity. The hypoconulid is a transverse ridge at the rear of the tooth, being connected with the entoconid by a strong postcristid. The m3 is little worn and displays several additional minor cuspules on the occlusal surface; these structures would be quickly removed with wear (fig. 3). The m3 differs from m1 and m 2 in having a longer talonid and a more pronounced hypoconulid. However, compared to those of G. elkema and G. ellae, the talonid of G. shevyrevae is relatively shorter and the hypoconulid is reduced; it does not form a projection at the posterior end of the tooth. The astragalus measures 11.34 mm long and 8.82 mm wide (maximum dimensions) and is partly broken at its head (fig. 4A). The morphology of the preserved portion is identical to that of Gomphos elkema (Meng et al., 2004). The bone is ventrodorsally (or anteroposteriorly) flat. The trochlea is transversely broad and shallow. In G. elkema, the lateral and medial rims of the astragalar trochlea appear to be more asymmetrical, with the lateral much larger than the medial (Meng et al., 2004). The calcaneus measures 20.8 mm long and 8.93 mm wide (maximum dimensions; fig. 4B). It is typical of Gomphos in that the calcaneoastragalar and sustentacular facets are aligned at the same level, similar to that of lagomorphs (Bleefeld and McKenna, 1985), but the bone lacks a calcaneal canal that is characteristic of lagomorphs (Bleefeld and Bock, 2002). The calcaneoastragalar facet is a narrow, long and convex surface in a proximodistal orientation, nearly parallel to the long axis of the bone, whereas the sustentacular facet is rounded and concave. Although the general morphology of the calcaneus is similar to that of G. elkema, it differs from the latter in having a facet on the distal side of the bone, which probably articulates with the navicular and astragalus. This feature does not occur in known astragali of G. elkema (Meng et al., 2004, 2005; Asher et al., 2005), and is most likely a derived feature of G. shevyrevae. However, in Mimolagus, a similar facet is present on the calcaneus, which is in articulation with the astragalus (Bohlin, 1951)., Published as part of Meng, Jin, Kraatz, Brian P., Wang, Yuanqing, Ni, Xijun, Gebo, Daniel L & Beard, K. Christopher, 2009, A New Species of Gomphos (Glires, Mammalia) from the Eocene of the Erlian Basin, Nei Mongol, China, pp. 1-12 in American Museum Novitates 3670 on pages 4-7, DOI: 10.1206/673.1, http://zenodo.org/record/4712995, {"references":["Meng, J., G. J. Bowen, J. Ye, P. L. Koch, S. - Y. Ting, Q. Li, and X. Jin. 2004. Gomphos elkema (Glires, Mammalia) from the Erlian Basin: evidence for the Early Tertiary Bumbanian Land Mammal Age in Nei-Mongol, China. American Museum Novitates 3425: 1 - 24.","Asher, R. J., J. Meng, M. C. McKenna, J. R. Wible, D. Dashzeveg, G. Rougier, and M. J. Novacek. 2005. Stem Lagomorpha and the antiquity of Glires. Science 307: 1091 - 1094.","Li, C. - K. 1977. Paleocene eurymyloids (Anagalida, Mammalia) of Quianshan, Anhui. Vertebrata Palasiatica 15: 103 - 118.","Li, C. - K., and S. - Y. Ting. 1993. New cranial and postcranial evidence for the affinities of the eurymylids (Rodentia) and mimotonids (Lagomorpha). In: F. S. Szalay, M. J. Novacek, and M. C. McKenna (editors), Mammal phylogeny: placentals: 151 - 158. New York: Springer.","Ting, S. - Y., J. Meng, M. C. McKenna, and C. - K. Li. 2002. The osteology of Matutinia (Simplicidentata, Mammalia) and its relationship to Rhombomylus. American Museum Novitates 3371: 1 - 33.","Meng, J., Y. - M. Hu, and C. - K. Li. 2003. The osteology of Rhombomylus (Mammalia, Glires): implications for phylogeny and evolution of Glires. Bulletin of the American Museum of Natural History 275: 1 - 247.","Meng, J., A. R. Wyss, M. R. Dawson, and R. - J. Zhai. 1994. Primitive fossil rodent from Inner Mongolia and its implications for mammalian phylogeny. Nature 370: 134 - 136.","Meng, J., X. - J. Ni, C. - K. Li, K. C. Beard, D. L. Gebo, Y. - Q. Wang, and H. - J. Wang. 2007 b. New material of Alagomyidae (Mammalia, Glires) from the late Paleocene Subeng locality, Inner Mongolia. American Museum Novitates 3597: 1 - 29.","Meng, J., and A. R. Wyss. 2001. The morphology of Tribosphenomys (Rodentiaformes, Mammalia): phylogenetic implications for basal Glires. Journal of Mammalian Evolution 8: 1 - 71.","Meng, J., C. - K. Li, X. - J. Ni, Y. - Q. Wang, and K. C. Beard. 2007 a. A new Eocene rodent from the lower Arshanto Formation in the Nuhetingboerhe (Camp Margetts) area, Inner Mongolia. American Museum Novitates 3569: 1 - 18.","Li, C. - K., J. - J. Zheng, and S. - Y. Ting. 1989. The skull of Cocomys lingchaensis, an Early Eocene Ctenodactyloid Rodent of Asia. In C. C. Black and M. R. Dawson (editors), Papers on fossil rodents in honour of Albert Elmer Wood. Natural History Museum of Los Angeles County Science Series 33: 179 - 192.","Kraatz, B. P., D. Badamgarav, and F. Bibi. 2009. Gomphos ellae, a new mimotonid from the Middle Eocene of Mongolia and its implications for the origin of Lagomorpha. Journal of Vertebrate Paleontology 29: 576 - 583.","Bleefeld, A. R., and M. C. McKenna. 1985. Skeletal integrity of Mimolagus rodens (Lagomorpha, Mammalia). American Museum Novitates 2806: 1 - 5.","Bleefeld, A. R., and W. J. Bock. 2002. Unique anatomy of lagomorph calcaneus. Acta Palaeontologica Polonica 47: 181 - 183.","Bohlin, B. 1951. Some mammalian remains from Shi-her-ma-cheng, Hui-hui-pu area, western Kansu. Report from the scientific expedition to the northwestern provinces of China under leadership of Dr. Sven Hedin. Vertebrate Palaeontology 5: 1 - 47."]}

Gomphos shevyrevae, new species HOLOTYPE: A right M1 (IVPP V 14669). PARATYPE: A right m1 (IVPP V 14670). INCLUDED SPECIMENS: A right P4 (or P3) (V14671.1), a right M1 (V14671.2), a right M2 (V14671.3), a left M2 (V14671.4), a right m1 (V14672.1), a right m2 (V14672.2), a left m3 (V14672.3), a left calcaneus (V14673), and a left astragalus (V14674). ETYMOLOGY: The species name is in honor of N.S. Shevyreva who named Gomphos elkema. DIAGNOSIS: Differs from Gomphos elkema and G. ellae in having more robust teeth with higher crowns, inflated cusps; upper molars with more posteriorly expanded hypocone and shelf; absence of the ridge connecting the lingual and labial cusps on P4; lower molars with relatively long trigonid and short talonid, reduced mesoconid and hypoconulid, and absence of the mesostylid; further differs from G. elkema in having extra facets on the calcaneus for articulation with the astragalus and navicular (unknown for G. ellae). TYPE LOCALITY AND AGE: Huheboerhe escarpment, Erlian Basin of Nei-Mongol, Middle Eocene lower beds of the Irdin Manha Formation. COMPARATIVE DESCRIPTION: Measurements of all teeth are in table 1. The tooth we identified as a P4 could also be a P3 (fig. 2). However, the anterior border of P3 is usually narrower than the posterior border in Gomphos. This tooth has its anterior portion TABLE 1 Tooth measurements of Gomphos shevyrevae (in mm) as wide as the posterior and bears a tiny posterolingual cusp, suggesting that it is likely a right P4. The P4 is a recently erupted tooth that bears no wear. As is typical of Gomphos, the P4 is unilaterally hypsodont and consists of a lingual main cusp, presumably the protocone, and a labial cusp. The lingual cusp is crescent shaped, and its two lophs form the anterior and posterior edges of the tooth. The labial cusp is conical, having a steeper labial surface and a more rounded lingual surface. Unlike P4 of Gomphos elkema, in which P4 is known (Meng et al., 2004; Asher et al., 2005), the ridge connecting the two cusps is absent in G. shevyrevae; instead, there is a weak ridge extending from the labial cusp anterolingually to join the midpoint of the anterior loph. The absence of a connection between the lingual and labial cusps of P4 recalls the condition found in Mimotona (Li, 1977; Li and Ting, 1993). Upper molars have one major lingual and two minor labial roots. The enamel is thick. M1 is so assigned because its hypocone and shelf are less expanded posteriorly than those of M2, and M1 is usually proportionally shorter than M2 (fig. 2). M1 of G. shevyrevae is similar to that of G. elkema in general morphology. However, the M1 and other upper cheek teeth of G. shevyrevae are more robust with more inflated cusps and stronger lophs. The protocone and its anterior and posterior lophs form a V-shaped structure with a slightly rounded apex (the lingual side of the protocone). The angle created by the lophs is about 45 °. The lingual portion of the anterior loph may be homologized with the preprotocrista and the labial portion, which is much thinner, with the preparaconule crista. A paraconule (protoconule) is not distinct, but is indicated by a slight inflation where the postparaconule crista joins the anterior loph. Absence of the paraconule is common in basal Glires, both in simplicidentates, such as Matutinia and Rhombomylus (Ting et al., 2002; Meng et al., 2003), and duplicidentates, such as Mimotona and Gomphos (Li, 1977; Li and Ting, 1993; Meng et al., 2004), but it is usually present in taxa that are more closely related to rodents and in basal rodents, such as Tribosphenomys (Meng et al., 1994, 2007b; Meng and Wyss, 2001), Neimengomys (Meng et al., 2007b), Archetypomys (Meng et al., 2007a), and Cocomys (Li et al., 1989). There is a weak ridge between the paracone and the anterior loph, which is probably the postparaconule crista. The metacone is small- er and more lingually positioned than the paracone. It is connected with the protocone by the posterior loph of the protocone. The latter loph is strong, almost as wide as the metacone. A mesostyle occurs at the posterior base of the paracone, which blocks the labial exit of the narrow trigon basin. The metaconule is present, but is difficult to distinguish in heavily worn specimens. In lightly worn specimens (fig. 2E) a broader wear facet indicates the metaconule that must be higher and broader than the crista in order for such a wear pattern to be created. In G. elkema the posterior loph of the protocone is relatively slimmer and there is usually a restriction labial to the protocone. The hypocone and the postcingulum are well developed, and both structures are expanded posteriorly. The hypocone is separated from the protocone by a transverse groove, and a similar condition occurs on M2. This condition appears to differ from the morphology prevailing in G. elkema and G. ellae. In well-worn specimens (fig. 2C), however, the protocone and hypocone become confluent. On the lingual surface of the tooth, a vertical groove between the protocone and hypocone exists near the occlusal surface of the tooth, and this feature also seems more pronounced than on upper molars of G. elkema and G. ellae. M2 is similar to M 1 in general morphology, but it is proportionally longer. The mesostyle is reduced, either being incorporated into the posterior base of the paracone or entirely absent. No M3 was collected. The lower molars have an anterior and a posterior root. The tooth crown is somewhat higher than that of G. elkema and G. ellae. As in the upper molars, the enamel appears thicker than that of G. elkema and G. ellae. The m1 is identified as such because it has a transversely oriented, ridgelike hypoconulid (fig 3). In Gomphos, the lower molar hypoconulid becomes more pronounced posteriorly. The m1 and m2 are very similar except that m2 has a more posteriorly projecting hypoconulid. The lower molars are proportionally wider, and therefore relatively shorter, than those of other species of the genus. Lower molar trigonids are proportionally longer in relation to their corresponding talonid than is the case in other species of the genus. As is typical of Gomphos, the protoconid and metaconid are transversely aligned, and the trigonid has nearly vertical anterior and posterior walls. The protoconid and the metaconid are subequal in size. The protoconid is worn more extensively and is therefore lower than the metaconid. The protoconid sends the paralophid (paracristid) to the anterolingual base of the metaconid and the protolophid (protocristid) to the posterior base of the metaconid. A crescentic trigonid basin is enclosed by the trigonid cusps and lophids. Lower molar talonids are as wide as the trigonid and are longer than their corresponding trigonid. The hypoconid is as large as the protoconid and is very close to the posterior wall of the trigonid, so that the hypoflexid becomes a narrow groove. The cristid obliqua (ectolophid) is short and the mesoconid appears very weak relative to other mimotonids. The entoconid is low. Unlike the condition in G. elkema and G. ellae, in which a mesostylid is present (Meng et al., 2004; Kraatz et al., 2009), the mesostylid is absent in the new species. Because of the reduction of the mesoconid and cristid obliqua, the talonid basin is a broad, featureless concavity. The hypoconulid is a transverse ridge at the rear of the tooth, being connected with the entoconid by a strong postcristid. The m3 is little worn and displays several additional minor cuspules on the occlusal surface; these structures would be quickly removed with wear (fig. 3). The m3 differs from m1 and m 2 in having a longer talonid and a more pronounced hypoconulid. However, compared to those of G. elkema and G. ellae, the talonid of G. shevyrevae is relatively shorter and the hypoconulid is reduced; it does not form a projection at the posterior end of the tooth. The astragalus measures 11.34 mm long and 8.82 mm wide (maximum dimensions) and is partly broken at its head (fig. 4A). The morphology of the preserved portion is identical to that of Gomphos elkema (Meng et al., 2004). The bone is ventrodorsally (or anteroposteriorly) flat. The trochlea is transversely broad and shallow. In G. elkema, the lateral and medial rims of the astragalar trochlea appear to be more asymmetrical, with the lateral much larger than the medial (Meng et al., 2004). The calcaneus measures 20.8 mm long and 8.93 mm wide (maximum dimensions; fig. 4B). It is typical of Gomphos in that the calcaneoastragalar and sustentacular facets are aligned at the same level, similar to that of lagomorphs (Bleefeld and McKenna, 1985), but the bone lacks a calcaneal canal that is characteristic of lagomorphs (Bleefeld and Bock, 2002). The calcaneoastragalar facet is a narrow, long and convex surface in a proximodistal orientation, nearly parallel to the long axis of the bone, whereas the sustentacular facet is rounded and concave. Although the general morphology of the calcaneus is similar to that of G. elkema, it differs from the latter in having a facet on the distal side of the bone, which probably articulates with the navicular and astragalus. This feature does not occur in known astragali of G. elkema (Meng et al., 2004, 2005; Asher et al., 2005), and is most likely a derived feature of G. shevyrevae. However, in Mimolagus, a similar facet is present on the calcaneus, which is in articulation with the astragalus (Bohlin, 1951).

Gomphos Shevyreva, 1975 TYPE SPECIES: Gomphos elkema Shevyreva, 1975. INCLUDED SPECIES: Gomphos ellae and G. shevyrevae, new species. REVISED DIAGNOSIS: Similar to other mimotonids but differing from other Glires in having two pairs of lower incisors. Differs from Mimotona (Li, 1977) in its larger size, less transversely extended and more unilaterally hypsodont upper teeth, stronger lophs, a mesostyle usually present, lower molars with a longer trigonid, and a mesoconid on lower molars. Differs from Anatolmylus (Averianov, 1994; Averianov and Godinot, 1998) in having a shallow horizontal ramus. Differs from Mimolagus (Bolin, 1951) in its smaller size and higher-crowned cheek teeth with distinctive cusps and ridges. LOCALITIES AND AGE: Gomphos elkema is known from Bumbanian faunas in Tsagan- Khushu, Nemegt Basin, and Ulan-Nur Basin of Mongolia (Dashzeveg and Russell, 1988; Dashzeveg, 1988); Huheboerhe, Wulanboerhe, and Nuhetingboerhe (Meng et al., 2004), and Bayan Ulan (Meng et al., 2005) in the Erlian Basin of Nei-Mongol (Inner Mongolia), China. G. ellae is from Tsagaan Khutel, Mongolia (Kraatz et al., 2009). G. shevyrevae is from the Irdin Manha Formation at Huheboerhe, Erlian. Early to Middle Eocene., Published as part of Meng, Jin, Kraatz, Brian P., Wang, Yuanqing, Ni, Xijun, Gebo, Daniel L & Beard, K. Christopher, 2009, A New Species of Gomphos (Glires, Mammalia) from the Eocene of the Erlian Basin, Nei Mongol, China, pp. 1-12 in American Museum Novitates 3670 on pages 3-4, DOI: 10.1206/673.1, http://zenodo.org/record/4712995, {"references":["Shevyreva, N. S., V. M. Chkhikvadze, and V. I. Zhegallo. 1975. New data on the vertebrate fauna of the Gashato Formation, Mongolian People's Republic. Bulletin of the Georgian Academy of Science 77: 225 - 228.","Li, C. - K. 1977. Paleocene eurymyloids (Anagalida, Mammalia) of Quianshan, Anhui. Vertebrata Palasiatica 15: 103 - 118.","Averianov, A. O. 1994. Early Eocene mimotonids of Kyrgyzstan and the problem of Mixodontia. Acta Palaeontologica Polonica 39: 393 - 411.","Averianov, A. O., and M. Godinot. 1998. A report on the Eocene Andarak mammal fauna of Kyrgyzstan. In K. C. Beard and M. R. Dawson (editors), Dawn of the age of mammals in Asia. Bulletin of Carnegie Museum of National History 34: 124 - 147.","Dashzeveg, D., and D. E. Russell. 1988. Palaeocene and Eocene Mixodontia (Mammalia, Glires) of Mongolia and China. Palaeontology 31: 129 - 164.","Meng, J., G. J. Bowen, J. Ye, P. L. Koch, S. - Y. Ting, Q. Li, and X. Jin. 2004. Gomphos elkema (Glires, Mammalia) from the Erlian Basin: evidence for the Early Tertiary Bumbanian Land Mammal Age in Nei-Mongol, China. American Museum Novitates 3425: 1 - 24.","Kraatz, B. P., D. Badamgarav, and F. Bibi. 2009. Gomphos ellae, a new mimotonid from the Middle Eocene of Mongolia and its implications for the origin of Lagomorpha. Journal of Vertebrate Paleontology 29: 576 - 583."]}

Distylomys Wang, 1988 TYPE SPECIES: Distylomys tedfordi Wang, 1988. INCLUDED SPECIES: Distylomys qianlishanensis Wang, 1988; D. burqinensis, n. sp. GEOLOGICAL RANGE: Late Oligocene to middle Miocene. GEOGRAPHIC DISTRIBUTION: Inner Mongolia, Gansu, and Xinjiang, China. EMENDED DIAGNOSIS: Incisive foramen small; tooth rows convergent anteriorly; mental foramen in diastema; distinct ventral masseteric crest extending below p4; sciurognathous angular process; dental formula 1/1, 0/0, 1/1, 3/3; cheek teeth hypselodont with asymmetrical pattern; P4 nonmolariform; upper molars bilophodont without the mure; p4 molariform; lower molars bilophodont with the mure; mesoflexid and hypoflexid deep and wide, opposite to each other and with cement; worn occlusal surface of cheek teeth smoothly concave with enamel thin or interrupted at the posterior edge of teeth., Published as part of Bi, Shundong, Meng, Jin, Wu, Wenyu, Ye, Jie & Ni, Xijun, 2009, New Distylomyid Rodents (Mammalia: Rodentia) from the Early Miocene Suosuoquan Formation of Northern Xinjiang, China, pp. 1-20 in American Museum Novitates 3663 on page 4, DOI: 10.1206/665.1, http://zenodo.org/record/4735501, {"references":["Wang, B. - Y. 1988. Distylomyidae fam. nov. (? Ctenodactyloidea, Rodentia) from Nei Mongol, China. Vertebrata Palasiatica 26 (1): 35 - 49."]}

Prodistylomys lii, n. sp. Figures 6–7, table 1 HOLOTYPE: IVPP V16015.1, right fragmentary mandible with broken i2, and m1–m3. REFERRED MATERIAL: IVPP V 16015.2, right M3; V 16015.3, right p4. STRATIGRAPHIC AND GEOGRAPHIC PROVENANCE: Suosuoquan Formation of Chibaerwoyi, Xinjiang. Early Miocene. ETYMOLOGY: Named for Professor Li Chuankui for his many contributions to the study of Asiatic rodents. DIAGNOSIS: Similar to P. xinjiangensis in size, but differs in having well-developed roots, the absence of the metaflexid, and less hypsodonty. COMPARATIVE DESCRIPTION: The only preserved upper cheek tooth V16015.2 is a heavily worn M3 (fig. 7–A). The M3 trigon is kidney shaped, whereas it is trapezoidal in Distylomys burqinensis. The talon is much narrower than the trigon. At this stage of wear, the flexi are already fused and form a fossette. No cement is present in the fossette. The two strong roots of M3 are fused. The mandible (fig. 6) is similar to that of the type species, P. xinjiangensis. The diastema is short and shallow. The mental foramen opens dorsally and lies on the dorsal side of the diastema. In contrast, in P. xinjiangensis the mental foramen opens labially and occurs near the level of the dorsal shelf. The lower incisor is short, extending posteriorly to below m2 as in P. xinjiangensis and D. qianlishanensis, whereas it extends as far as m 3 in D. burqinensis. The tip of the lower incisor is broken and its cross section is subrectangular with flat anterior and lingual walls. The enamel thins and extends a short distance onto the labial and lingual walls. The p4 is not preserved in the holotype, but the alveolus indicates presence of three roots (fig. 6). The only known p4 is IVPP V16015.3 (fig. 7B). The trigonid is shaped like an isosceles triangle with gently concave labial and lingual margins. The anterolophid is short and blunt. The hypoflexid extends only halfway down the tooth, whereas the mesoflexid is much longer, extending to the root. The flexids are U-shaped and have no cement. In P. xinjiangensis, the flexids are V-shaped and cement filled. The talonid is wider than the trigonid; the talonid is slightly broken posteriorly, but what remains suggests absence of a metaflexid. This p4 has 3 roots. Although the p4 crown morphology is similar to that of dp4 of P. xinjiangensis except for the absence of the posterolophid, we prefer to consider this tooth as p4 because the roots are not splayed apart. If so interpreted, it is probable that p4 and dp4 have similar general crown morphology. The lower molars have the same bilophodont occlusal pattern as P. xinjiangensis, but lack the posterolophid. The flexids extend only to the alveolus, clearly showing welldeveloped roots in all the lower molars. In P. xinjiangensis, the flexids extend all the way into the tooth base, indicating reduced roots. COMMENTS: In the Chibaerwoyi locality, fossils were mostly collected from beds A and B (7–12 m, and 14–21 m from the base of the formation, respectively). P. lii was collected from Bed A. The exact stratigraphic level of P. xinjiangensis was uncertain, but most likely was collected from Bed A. However, P. lii is morphologically more primitive than P. xinjiangensis in having stronger roots, or less hypsodonty, and lack of posterolophid, suggesting an earlier occurrence.

Distylomys burqinensis, n. sp. Figures 2���5, table 1 DIAGNOSIS: Intermediate sized species, slightly larger than D. tedfordi and smaller than D. qianlishanensis. Differing from D. tedfordi in having p4 longer than m1, a more elongate anterolophid and absence of posterolophid on p4, m1 relatively wider with a more acute lingual apex of the trigonid. Differs from D. qianlishanensis in having a more acute anterolophid and subtriangular talonid on p4, lower molar trigonid triangular, and mental foramen higher on the mandible. HOLOTYPE: IVPP V16014.1, anterior partial skull with P4���M3 and associated mandible. REFERRED MATERIAL: IVPP V 16014.2, palate with dentition; V 16014.3, palate with broken left P4���M2 and right M1���M3; V 16014.4, palate with left M1���M2 and right P4���M2; V 16014.5, palate with left M1 and right M1���M2; V 16014.6, partial premaxilla with incisors; V 16014.7, left premaxilla with broken I2; V 16014.8���9, 2 right premaxillae with broken I2; V 16014.10���14, 5 left M1; V 16014.15, left M2; V 16014.16���21, 6 right M1; V 16014.22, right M2; V 16014.23���26, 4 right M3; V 16014.27���32, 6 left fragmentary mandibles with broken i2, and p4���m3; V 16014.33���34, 2 left fragmentary mandibles with broken i2 and p4���m2; V 16014.35���39, 5 left fragmentary mandibles with p4���m1; V 16014.40, left fragmentary mandible with p4; V 16014.41, left fragmentary mandible with broken p4���m1; V 16014.42, left fragmentary mandible with m1���m2; V 16014.43, left fragmentary mandible with m2���m3; V 16014.44, left m1; V 16014.45���46, 2 left m2; V 16014.47, left m3; V 16014. 48, right fragmentary mandible with broken i2 and p4���m3; V 16014.49, right fragmentary mandible with broken p4 ���m1 and complete m2���m3; V 16014.50���51, 2 right fragmentary mandibles with p4���m2; V 16014.52��� 55, 4 right fragmentary mandibles with p4; V 16014.56���57, 2 right fragmentary mandibles with m1���m2; V 16014.58, right fragmentary mandible with m2���m3; V 16014.59, right fragmentary mandible with broken m1; V 16014.60���61, 2 right p4; V 16014.62���64, 3 right m1; V 16014.65���66, 2 right m3. ETYMOLOGY: the species name refers to Burqin County, where site XJ200601 is located. LOCALITY AND AGE: Locality XJ200601 (47 �� 23.198 9 N, 86 �� 47.981 9 E), Burqin County, Xinjiang, China. Suosuoquan Formation, early Miocene. REPOSITORY: The specimens are stored in the collections of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing. DESCRIPTION: The holotype IVPP V16014.1 is a partial skull with articulated mandible. The skull preserves the anterior half, including the rostrum, palate, and partial frontal (fig. 2) and has been crushed and distorted, with the premaxilla shifted slightly lateroventrally. The incisive foramen is obscured due to distortion. Judging from what is preserved in the holotype and V16014.2 (fig. 4), it is very slender and narrow and ends posteriorly at the level of the center of the anterior zygomatic root. The base of the zygomatic root is preserved and shows that the zygomatic plate is not developed; its anterior margin is located far in front of P4 and its posterior margin is between P4 and M1. The tooth rows are convergent anteriorly. The palate is wider than the length of m1. The palatine-maxillary suture starts from anterior to M1. No palatine foramen can be recognized. In dorsal view, the nasal bones are narrow and extend posteriorly as far as the premaxillae. Laterally, the premaxillary-maxillary suture extends above M1. The infraorbital foramen, although broken, is evidently large and hystricomorphous. The frontals are flat and broadened relative to the width of the rostrum. The diastema of the mandible is shallow and shorter than the tooth row (fig. 3). The mental foramen is small and near the dorsal surface of the diastema. The mandible has a robust ventral masseteric crest, but there is no trace for the dorsal crest. The ventral crest terminates slightly anterior to the talonid of p4. Very little of the ascending ramus and angular process is preserved, but what remains suggests that the angular process is in the plane of the incisor within the horizontal ramus, as in other distylomyids. The dental formula is 1/1, 0/0, 1/1, 3/3. All cheek teeth are hypselodont and at least moderately worn, so that little is known about tooth cusps. The upper incisors are broad and flattened anteriorly. Upper cheek teeth are strongly recurved toward the root, and the curvature increases posteriorly (fig. 4). P4 is nonmolariform, unilobate, and somewhat trapezoidal in occlusal outline, with the posterior border slightly wider than the anterior one (fig. 4). Enamel is thinner at posterior margin. All upper molars are strongly bilophodont without the mure, so that the trigon and talon form two separated enamel loops. The trigon and talon are straight and parallel to each other. They are separated by a transverse central flexus, which is almost completely filled with cement. In side views, lateral and medial flexi persist to the base of the tooth crown. The trigon is trapezoidal with a flattened lingual wall and a gently convex labial one. The talon is subrectangular, slightly wider than long. Given the tooth curvature, the upper tooth crown inclines posteriorly. Each molar bears four transverse enamel lophs that form the cutting edges of the tooth. M1 is on average larger than M2 (table 1). In M1, the talon is wider but anteroposteriorly more compressed than the trigon. In M2 the talon is equal to or narrower than the trigon. M3 is larger than the preceding molars. In M3, the talon is reduced and much narrower, but slightly longer than the trigon. The lower incisors extend posteriorly in the jaw to below m3 (fig. 3). The incisor enamel is thick, relative to the depth of the incisor (fig. 5D���F). It has a flat buccal surface and similarly wraps around to cover the medial and lateral sides of the tooth to a significant extent. The enamel microstructure is multiserial (Korvenkontio, 1934; Wahlert, 1968, 1989; Martin, 1992, 1997), and more specifically it consists of multiserial Hunter-Schreger bands (HSB) with rectangular interprismatic matrix (IPM), a more derived type than the parallel IPM that has an acute angle to the bands (Martin, 1992; 1997). The enamel is 150��� 165 Mm thick, of which the portio interna (PI) and portio externa (PE) account for about 85% and 15%, respectively. Within the PI, each band consists mostly of four prisms. The HSB has a 50 �� ���60 �� angle to the enamel-dentine junction, as measured following Martin (1992). Unlike P4, which is nonmolariform, p4 is fully molariform and the largest of lower cheek teeth (fig. 4). The p4 trigonid is narrower than the talonid, with an acute anterior projection; its anterolingual edge is concave. The talonid is shorter but wider than the trigonid. No posterolophid is present except for three specimens that bear a shallow one. In 11 mandibles with check teeth, the premolar is less worn or in the same stage of wear as m1. Therefore we identify it as permanent p4, although Wang (1997) suggested that it may be deciduous p4. All lower molars are similar in overall morphology. The m1 is longer than m2, but shorter than m3. All molars are bilophodont but have the mure; therefore, the trigonid and talonid are confluent through a narrow neck. The trigonid is triangular, with a tapered and acute lingual apex and straight anterolingual edge. The mesoflexid and hypoflexid intrude transversely halfway across the crown and are filled by thin cement. In side view, both flexids extend to the base of the crown. In m1, the talonid is wider than the trigonid with gently convex posterior edge. In m2, the talonid is equal to or slightly narrower than the trigonid. In m3, the talonid is much narrower than the trigonid. COMMENT: The type species D. tedfordi was described by Wang (1988) on the basis of a single mandible, which was collected in 1928 by the Third Asiatic Expedition, AMNH, from the middle Miocene Tunggur Formation of the Tairum Nor Basin of Inner Mongolia. No additional material has since been referred to the species, restricting the comparison of the new materials to the lower jaw only. D. burqinensis is similar to D. tedfordi and is clearly closely related to it. The type specimen of D. tedfordi from Tunggur lies within the lower size range of D. burqinensis from Burqin. Morphologically, however, D. tedfordi differs from D. burqinensis in several aspects: p4 shorter than m1, having a less elongate anterolophid and subelliptical talonid, m1 relatively narrower with an inward curved anterolingual edge and more blunt lingual apex. In D. tedfordi, the posterolophid is distinct on p4; in Burqin specimens, it is distinct in three, and absent in eight. D. burqinensis is smaller than D. qianlishanensis and differs in having a more acute anterolophid and subtriangular talonid on p4; triangular trigonid on lower molars, and higher position of the mental foramen on the mandible. Wang (1988) thought D. tedfordi was morphologically more primitive than D. qianlishanensis because it possesses a well-developed posterolophid, a condition considered primitive. This, as Wang noted, is inconsistent with the stratigraphic occurrences of the species because D. tedfordi was found in later deposits (middle Miocene) than D. qianlishanensis (late Oligocene). D. burqinensis, with an early Miocene age, also lacks the posterolophid or has only an incipient one. We therefore offer an alternative interpretation: the presence of the posterolophid is a derived character within the genus, appearing in species with a younger age. If this is true, D. burqinensis is morphologically intermediate between D. qianlishanensis and D. tedfordi, but is more similar to the latter. It should be noted that size decreases in this lineage., Published as part of Bi, Shundong, Meng, Jin, Wu, Wenyu, Ye, Jie & Ni, Xijun, 2009, New Distylomyid Rodents (Mammalia: Rodentia) from the Early Miocene Suosuoquan Formation of Northern Xinjiang, China, pp. 1-20 in American Museum Novitates 3663 on pages 4-11, DOI: 10.1206/665.1, http://zenodo.org/record/4735501, {"references":["Korvenkontio, V. A. 1934. Mikroskopische Untersuchungen an Nagerincisiven unter Hinweis auf die Schmelzstruktur der Backenzahne. Annales Zoologici Societatis Zoologicae-Botanicae Fennicae ' Vanamo' 2: 1 - 274.","Wahlert, J. H. 1968. Variability of rodent incisor enamel as viewed in thin section, and the microstructure of the enamel in fossil and Recent rodent groups. Breviora of the Museum of Comparative Zoology 309: 1 - 18.","Wahlert, J. H. 1989. The three types of incisor enamel in rodents. In C. C. Black and M. R. Dawson (editors), Papers on fossil rodents in honor of Albert Elmer Wood. Natural History Museum of Los Angeles County Science Series 33: 7 - 16.","Martin, T. 1992. Schmelzmikrostructur in den incisiven alt- und neuweltlicher hystricognather Nagetiere. Palaeovertebrata Memoire Extraordinaire: 1 - 168.","Martin, T. 1997. Incisor enamel microstructure and systematics in rodents. In W. V. Koenigswald and P. M. Sander (editors), Tooth enamel microstructure, 163 - 175. Rotterdam: Balkema.","Wang, B. - Y. 1997. The mid-Tertiary Ctenodactyloidea (Rodentia, Mammalia) of eastern and central Asia. Bulletin of the American Museum of Natural History 234: 1 - 88.","Wang, B. - Y. 1988. Distylomyidae fam. nov. (? Ctenodactyloidea, Rodentia) from Nei Mongol, China. Vertebrata Palasiatica 26 (1): 35 - 49."]}

Distylomys burqinensis, n. sp. Figures 2–5, table 1 DIAGNOSIS: Intermediate sized species, slightly larger than D. tedfordi and smaller than D. qianlishanensis. Differing from D. tedfordi in having p4 longer than m1, a more elongate anterolophid and absence of posterolophid on p4, m1 relatively wider with a more acute lingual apex of the trigonid. Differs from D. qianlishanensis in having a more acute anterolophid and subtriangular talonid on p4, lower molar trigonid triangular, and mental foramen higher on the mandible. HOLOTYPE: IVPP V16014.1, anterior partial skull with P4–M3 and associated mandible. REFERRED MATERIAL: IVPP V 16014.2, palate with dentition; V 16014.3, palate with broken left P4–M2 and right M1–M3; V 16014.4, palate with left M1–M2 and right P4–M2; V 16014.5, palate with left M1 and right M1–M2; V 16014.6, partial premaxilla with incisors; V 16014.7, left premaxilla with broken I2; V 16014.8–9, 2 right premaxillae with broken I2; V 16014.10–14, 5 left M1; V 16014.15, left M2; V 16014.16–21, 6 right M1; V 16014.22, right M2; V 16014.23–26, 4 right M3; V 16014.27–32, 6 left fragmentary mandibles with broken i2, and p4–m3; V 16014.33–34, 2 left fragmentary mandibles with broken i2 and p4–m2; V 16014.35–39, 5 left fragmentary mandibles with p4–m1; V 16014.40, left fragmentary mandible with p4; V 16014.41, left fragmentary mandible with broken p4–m1; V 16014.42, left fragmentary mandible with m1–m2; V 16014.43, left fragmentary mandible with m2–m3; V 16014.44, left m1; V 16014.45–46, 2 left m2; V 16014.47, left m3; V 16014. 48, right fragmentary mandible with broken i2 and p4–m3; V 16014.49, right fragmentary mandible with broken p4 –m1 and complete m2–m3; V 16014.50–51, 2 right fragmentary mandibles with p4–m2; V 16014.52– 55, 4 right fragmentary mandibles with p4; V 16014.56–57, 2 right fragmentary mandibles with m1–m2; V 16014.58, right fragmentary mandible with m2–m3; V 16014.59, right fragmentary mandible with broken m1; V 16014.60–61, 2 right p4; V 16014.62–64, 3 right m1; V 16014.65–66, 2 right m3. ETYMOLOGY: the species name refers to Burqin County, where site XJ200601 is located. LOCALITY AND AGE: Locality XJ200601 (47 ° 23.198 9 N, 86 ° 47.981 9 E), Burqin County, Xinjiang, China. Suosuoquan Formation, early Miocene. REPOSITORY: The specimens are stored in the collections of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing. DESCRIPTION: The holotype IVPP V16014.1 is a partial skull with articulated mandible. The skull preserves the anterior half, including the rostrum, palate, and partial frontal (fig. 2) and has been crushed and distorted, with the premaxilla shifted slightly lateroventrally. The incisive foramen is obscured due to distortion. Judging from what is preserved in the holotype and V16014.2 (fig. 4), it is very slender and narrow and ends posteriorly at the level of the center of the anterior zygomatic root. The base of the zygomatic root is preserved and shows that the zygomatic plate is not developed; its anterior margin is located far in front of P4 and its posterior margin is between P4 and M1. The tooth rows are convergent anteriorly. The palate is wider than the length of m1. The palatine-maxillary suture starts from anterior to M1. No palatine foramen can be recognized. In dorsal view, the nasal bones are narrow and extend posteriorly as far as the premaxillae. Laterally, the premaxillary-maxillary suture extends above M1. The infraorbital foramen, although broken, is evidently large and hystricomorphous. The frontals are flat and broadened relative to the width of the rostrum. The diastema of the mandible is shallow and shorter than the tooth row (fig. 3). The mental foramen is small and near the dorsal surface of the diastema. The mandible has a robust ventral masseteric crest, but there is no trace for the dorsal crest. The ventral crest terminates slightly anterior to the talonid of p4. Very little of the ascending ramus and angular process is preserved, but what remains suggests that the angular process is in the plane of the incisor within the horizontal ramus, as in other distylomyids. The dental formula is 1/1, 0/0, 1/1, 3/3. All cheek teeth are hypselodont and at least moderately worn, so that little is known about tooth cusps. The upper incisors are broad and flattened anteriorly. Upper cheek teeth are strongly recurved toward the root, and the curvature increases posteriorly (fig. 4). P4 is nonmolariform, unilobate, and somewhat trapezoidal in occlusal outline, with the posterior border slightly wider than the anterior one (fig. 4). Enamel is thinner at posterior margin. All upper molars are strongly bilophodont without the mure, so that the trigon and talon form two separated enamel loops. The trigon and talon are straight and parallel to each other. They are separated by a transverse central flexus, which is almost completely filled with cement. In side views, lateral and medial flexi persist to the base of the tooth crown. The trigon is trapezoidal with a flattened lingual wall and a gently convex labial one. The talon is subrectangular, slightly wider than long. Given the tooth curvature, the upper tooth crown inclines posteriorly. Each molar bears four transverse enamel lophs that form the cutting edges of the tooth. M1 is on average larger than M2 (table 1). In M1, the talon is wider but anteroposteriorly more compressed than the trigon. In M2 the talon is equal to or narrower than the trigon. M3 is larger than the preceding molars. In M3, the talon is reduced and much narrower, but slightly longer than the trigon. The lower incisors extend posteriorly in the jaw to below m3 (fig. 3). The incisor enamel is thick, relative to the depth of the incisor (fig. 5D–F). It has a flat buccal surface and similarly wraps around to cover the medial and lateral sides of the tooth to a significant extent. The enamel microstructure is multiserial (Korvenkontio, 1934; Wahlert, 1968, 1989; Martin, 1992, 1997), and more specifically it consists of multiserial Hunter-Schreger bands (HSB) with rectangular interprismatic matrix (IPM), a more derived type than the parallel IPM that has an acute angle to the bands (Martin, 1992; 1997). The enamel is 150– 165 Mm thick, of which the portio interna (PI) and portio externa (PE) account for about 85% and 15%, respectively. Within the PI, each band consists mostly of four prisms. The HSB has a 50 ° –60 ° angle to the enamel-dentine junction, as measured following Martin (1992). Unlike P4, which is nonmolariform, p4 is fully molariform and the largest of lower cheek teeth (fig. 4). The p4 trigonid is narrower than the talonid, with an acute anterior projection; its anterolingual edge is concave. The talonid is shorter but wider than the trigonid. No posterolophid is present except for three specimens that bear a shallow one. In 11 mandibles with check teeth, the premolar is less worn or in the same stage of wear as m1. Therefore we identify it as permanent p4, although Wang (1997) suggested that it may be deciduous p4. All lower molars are similar in overall morphology. The m1 is longer than m2, but shorter than m3. All molars are bilophodont but have the mure; therefore, the trigonid and talonid are confluent through a narrow neck. The trigonid is triangular, with a tapered and acute lingual apex and straight anterolingual edge. The mesoflexid and hypoflexid intrude transversely halfway across the crown and are filled by thin cement. In side view, both flexids extend to the base of the crown. In m1, the talonid is wider than the trigonid with gently convex posterior edge. In m2, the talonid is equal to or slightly narrower than the trigonid. In m3, the talonid is much narrower than the trigonid. COMMENT: The type species D. tedfordi was described by Wang (1988) on the basis of a single mandible, which was collected in 1928 by the Third Asiatic Expedition, AMNH, from the middle Miocene Tunggur Formation of the Tairum Nor Basin of Inner Mongolia. No additional material has since been referred to the species, restricting the comparison of the new materials to the lower jaw only. D. burqinensis is similar to D. tedfordi and is clearly closely related to it. The type specimen of D. tedfordi from Tunggur lies within the lower size range of D. burqinensis from Burqin. Morphologically, however, D. tedfordi differs from D. burqinensis in several aspects: p4 shorter than m1, having a less elongate anterolophid and subelliptical talonid, m1 relatively narrower with an inward curved anterolingual edge and more blunt lingual apex. In D. tedfordi, the posterolophid is distinct on p4; in Burqin specimens, it is distinct in three, and absent in eight. D. burqinensis is smaller than D. qianlishanensis and differs in having a more acute anterolophid and subtriangular talonid on p4; triangular trigonid on lower molars, and higher position of the mental foramen on the mandible. Wang (1988) thought D. tedfordi was morphologically more primitive than D. qianlishanensis because it possesses a well-developed posterolophid, a condition considered primitive. This, as Wang noted, is inconsistent with the stratigraphic occurrences of the species because D. tedfordi was found in later deposits (middle Miocene) than D. qianlishanensis (late Oligocene). D. burqinensis, with an early Miocene age, also lacks the posterolophid or has only an incipient one. We therefore offer an alternative interpretation: the presence of the posterolophid is a derived character within the genus, appearing in species with a younger age. If this is true, D. burqinensis is morphologically intermediate between D. qianlishanensis and D. tedfordi, but is more similar to the latter. It should be noted that size decreases in this lineage.

Prodistylomys Wang and Qi, 1989 TYPE SPECIES: Prodistylomys xinjiangensis Wang and Qi, 1989. INCLUDED SPECIES: Prodistylomys lii, n. sp.; P. wangae, n. sp. GEOLOGICAL RANGE: Early Miocene. GEOGRAPHIC DISTRIBUTION: Xinjiang, China EMENDED DIAGNOSIS: M3 bilophodont without the mure and asymmetrical with the corresponding lower molar, as in Distylomys. Differs from Distylomys in having rooted, hypsodont cheek teeth, M3 trigon semilunar shaped in outline, p4 with shorter trigonid, m1���2 with short trigonid and narrower talonid than the trigonid, thinner cement in hypoflexid and mesoflexid in lower molars., Published as part of Bi, Shundong, Meng, Jin, Wu, Wenyu, Ye, Jie & Ni, Xijun, 2009, New Distylomyid Rodents (Mammalia: Rodentia) from the Early Miocene Suosuoquan Formation of Northern Xinjiang, China, pp. 1-20 in American Museum Novitates 3663 on page 11, DOI: 10.1206/665.1, http://zenodo.org/record/4735501, {"references":["Wang, B. - Y., and T. Qi. 1989. Prodistylomys gen. nov. (Distylomyidae,? Ctenodactyloidea, Rodentia) from Xinjiang, China. Vertebrata Palasiatica 27 (1): 28 - 36."]}

Prodistylomys wangae, n. sp. Figure 8, table 1 HOLOTYPE: IVPP V16016.1, right fragmentary mandible with broken incisor and complete p4–m2. REFERRED MATERIAL: IVPP V 16016.2, right M3; V 16016.3, left fragmentary mandible with broken i2–p4, and m1–m2; V 16016.4, right fragmentary mandible with broken i2 and p4–m2; V 16016.5, left m1. LOCALITY AND AGE: Locality XJ200601 (47 ° 23.198 9 N, 86 ° 47.981 9 E) in Burqin County of Xinjiang, Suosuoquan Formation, early Miocene. ETYMOLOGY: The species name, wangae, is in honor of our colleague, Wang Banyue, for her contribution to the study of distylomyids. REPOSITORY: The specimens are stored in the collections of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing. DIAGNOSIS: Slightly larger than P. lii and P. xinjiangensis. Differs from P. lii in having weak roots, thicker cement, rounded lingual apex of m1 trigonid, shorter talonid on m2. Differs from P. xinjiangensis in having thicker cement, rounded lingual apex of m1 trigonid, and the absence of the metaflexid on lower molars. DESCRIPTION: The M3 trigon is semicircular in outline, with a straight posterior margin (fig. 8A). The enamel is very thick, becoming thinner on the posterior margin. The hypoflexus extends to the base of the crown and becomes shallower while approaching the base. The mesoflexus extends L of the height of the crown and is fused toward the base, suggesting a rudimentary root. On the contrary, in P. lii, both flexi are fused, showing a well-developed root. The talon is circular shaped, much narrower than the trigon. The state of the masseteric crest is typical for the genus; the ventral crest is strong and extends under p4 and the dorsal crest is absent. The lower incisor extends posteriorly to underneath m3. The lower incisor is similar in its general morphology and microstructure to that of Distylomys burqinensis except that the pulp cavity is significantly smaller (fig. 5A, D). The p4 is shorter than m1 (fig. 8C). The trigonid is much narrower than the talonid compared with that in P. lii and P. xinjiangensis and has a stout anterolophid. The anterolophid is blunt and lies well toward the labial side of the tooth rather than in the center. Only thin cement is present in the flexids. The talonid has a vestigial posterolophid. Only m1 and m2 are preserved (fig. 8C; table 1). The lower molars are bilophodont, and hypsodont. The crown expands toward the base. The trigonid is subelliptical with a rounded anterior wall and a long axis oriented slightly anterolabial-posterolingually. The flexids are Ushaped with thin cement; the mesoflexid shallows but extends all the way to the base, and the hypoflexid extends down 2/3 of the height of the crown where it closes, indicating a rudimentary root (fig. 8B). The talonid is narrower than the trigonid, and is compressed with acute labial and lingual angles. The m1 and m2 are identical in crown morphology, but m2 is shorter than m1, and the lingual apex of its trigonid is more acute. COMMENT: Although the Xinjiang specimens are very similar to Distylomys in crown morphology, the rudimentary roots of the cheek teeth, shorter trigonid and narrower talonid on lower molars, and thinner cement suggest that it is better to assign the specimens to the genus Prodistylomys rather than to Distylomys. P. wangae differs substantially from P. lii in showing a tendency to the loss of roots and subelliptical trigonid. It differs from P. xinjiangensis in the absence of the posterolophid (or metaflexid) and subelliptical trigonid.

Prodistylomys wangae, n. sp. Figure 8, table 1 HOLOTYPE: IVPP V16016.1, right fragmentary mandible with broken incisor and complete p4���m2. REFERRED MATERIAL: IVPP V 16016.2, right M3; V 16016.3, left fragmentary mandible with broken i2���p4, and m1���m2; V 16016.4, right fragmentary mandible with broken i2 and p4���m2; V 16016.5, left m1. LOCALITY AND AGE: Locality XJ200601 (47 �� 23.198 9 N, 86 �� 47.981 9 E) in Burqin County of Xinjiang, Suosuoquan Formation, early Miocene. ETYMOLOGY: The species name, wangae, is in honor of our colleague, Wang Banyue, for her contribution to the study of distylomyids. REPOSITORY: The specimens are stored in the collections of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing. DIAGNOSIS: Slightly larger than P. lii and P. xinjiangensis. Differs from P. lii in having weak roots, thicker cement, rounded lingual apex of m1 trigonid, shorter talonid on m2. Differs from P. xinjiangensis in having thicker cement, rounded lingual apex of m1 trigonid, and the absence of the metaflexid on lower molars. DESCRIPTION: The M3 trigon is semicircular in outline, with a straight posterior margin (fig. 8A). The enamel is very thick, becoming thinner on the posterior margin. The hypoflexus extends to the base of the crown and becomes shallower while approaching the base. The mesoflexus extends L of the height of the crown and is fused toward the base, suggesting a rudimentary root. On the contrary, in P. lii, both flexi are fused, showing a well-developed root. The talon is circular shaped, much narrower than the trigon. The state of the masseteric crest is typical for the genus; the ventral crest is strong and extends under p4 and the dorsal crest is absent. The lower incisor extends posteriorly to underneath m3. The lower incisor is similar in its general morphology and microstructure to that of Distylomys burqinensis except that the pulp cavity is significantly smaller (fig. 5A, D). The p4 is shorter than m1 (fig. 8C). The trigonid is much narrower than the talonid compared with that in P. lii and P. xinjiangensis and has a stout anterolophid. The anterolophid is blunt and lies well toward the labial side of the tooth rather than in the center. Only thin cement is present in the flexids. The talonid has a vestigial posterolophid. Only m1 and m2 are preserved (fig. 8C; table 1). The lower molars are bilophodont, and hypsodont. The crown expands toward the base. The trigonid is subelliptical with a rounded anterior wall and a long axis oriented slightly anterolabial-posterolingually. The flexids are Ushaped with thin cement; the mesoflexid shallows but extends all the way to the base, and the hypoflexid extends down 2/3 of the height of the crown where it closes, indicating a rudimentary root (fig. 8B). The talonid is narrower than the trigonid, and is compressed with acute labial and lingual angles. The m1 and m2 are identical in crown morphology, but m2 is shorter than m1, and the lingual apex of its trigonid is more acute. COMMENT: Although the Xinjiang specimens are very similar to Distylomys in crown morphology, the rudimentary roots of the cheek teeth, shorter trigonid and narrower talonid on lower molars, and thinner cement suggest that it is better to assign the specimens to the genus Prodistylomys rather than to Distylomys. P. wangae differs substantially from P. lii in showing a tendency to the loss of roots and subelliptical trigonid. It differs from P. xinjiangensis in the absence of the posterolophid (or metaflexid) and subelliptical trigonid., Published as part of Bi, Shundong, Meng, Jin, Wu, Wenyu, Ye, Jie & Ni, Xijun, 2009, New Distylomyid Rodents (Mammalia: Rodentia) from the Early Miocene Suosuoquan Formation of Northern Xinjiang, China, pp. 1-20 in American Museum Novitates 3663 on page 13, DOI: 10.1206/665.1, http://zenodo.org/record/4735501

Neimengomys qii, new spesies HOLOTYPE: IVPP V14711.1, a right M1 (or M2) (fig. 13b). INCLUDED SPECIMENS: V 14711.2, left P4; V 14711.3–10, 8 M1s and/or M2s; V 14711.11–14, 4 M3S (or M2s); V 14712.1, right p4; V 14712.2, right m1; V 14712.3–5, 14712.3–5, 3 m3s (fig. 13). See table 5 for measurements. ETYMOLOGY: The trivial name is after Qi Tao (IVPP), who made the first discovery of Tribosphenomys specimens by screenwashing at Subeng in the 1980s. DIAGNOSIS: Same as for the genus. TYPE LOCALITY AND AGE: Subeng, about 25 km west of Erlian, Gashatan, Late Paleocene. COMPARATIVE DESCRIPTION: A P4 is identified for this species (fig. 13a). This tooth is smaller than those of T. minutus and transversely oval-shaped. The P4 buccal shelf is much narrower than that of T. minutus and is similar to that of A. inopinatus (Dashzeveg, 1990b). It differs from both Tribosphenomys and Alagomys in bearing a very small cuspule on the buccal shelf. Nine upper cheek teeth are considered to be either M1 or M2 (fig. 13b–j), which we cannot yet distinguish with confidence. These teeth have an oval shape in occlusal view. Compared to M1 of Tribosphenomys minutus these teeth are narrower and less symmetrical along the transverse axis, the protocone is more inflated, the hypocone is more inflated and buccally positioned, and the buccal shelf of the tooth is distinctly narrower. The width/ length ratio of these teeth is similar to that of M2 of T. minutus, but M2 of T. minutus is more triangular in occlusal view, the anterior edge of the tooth is much wider than its posterior counterpart, the protocone is anteroposteriorly more compressed, and the hypocone is usually absent. These teeth are also distinctive in size and morphology from upper molars of T. secundus (Lopatin and Averianov, 2004a). The molars of Neimengomys qii differ from M1 and/or M2 of Alagomys in having a hypocone and a more prominent buccal shelf. Among species of Alagomys, N. qii is more comparable with the North American A. russelli than the Asian A. inopinatus and A. oriensis. The Asian species are similar in have an anteroposteriorly compressed protocone, while A. russelli has an inflated protocone and a somewhat oval-shaped occlusal outline (Dawson and Beard, 1996: plate 1F). Subeng specimens differ from A. russelli in having a distinct buccal shelf on the upper molars, whereas the same structure is completely absent in A. russelli. In addition, the molar cusps of A. russelli are less isolated, the lophs are stronger, the protocone is more inflated, and the trigon basin is deeper. In addition, the basin and postcingulum between the protocone and metaconule are more prominent in Subeng specimens. Four specimens are identified as M3s (fig. 13k–n) of Neimengomys qii because of their small size and reduced metacone. Compared to M3 of T. minutus, the M3 of N. qii is also oval-shaped and has a more inflated, conical protocone. The M3 of N. qii is more transverse and cuspate than those of Alagomys (Dawson and Beard, 1996; Tong and Dawson, 1995). However, we cannot rule out the possibility that these teeth are M2. One p4 is identified as N. qii because of its smaller size and unique morphology. Unlike those referred to T. minutus, the p4 (fig. 13o) has a narrow trigonid consisting of two closely appressed cusps. In contrast, the talonid is wider than the trigonid and formed by two transverse, ridgelike cuspids. The p4 is similar in morphology to that of T. secundus (Lopatin and Averianov, 2004a), but differs in being much smaller. The m1 of N. qii (fig. 13p) has a narrower trigonid than those of T. minutus and a hypoconulid that is aligned with the entoconid as a ridge. Three m3s are referred to T. qii (fig. 13q–s). The hypoconulid on these m3s is more transverse than conical, differing from those referred to T. minutus. The trigonid basin of the lower molar is somewhat restricted, similar to that of T. minutus. In contrast, the trigonid basin in Alagomys is more open. Although the material is fragmentary, the morphologies of these teeth show that they must be from a previously unknown taxon. Based on these specimens, we propose a new genus and species of alagomyid.

Neimengomys, new genus TYPE SPECIES: Neimengomys qii, new species ETYMOLOGY: Nei-Meng is Chinese (in pinyin) for ‘‘Inner Mongolia’’; mys is Greek for ‘‘mouse’’, in analogy with Alagomys and Tribosphenomys. DIAGNOSIS: Differs from Alagomys but resembles Tribosphenomys in having a buccal shelf and a hypocone on upper molars, a more transverse M3 with conical cusps, and a narrower talonid basin. Differs from Tribosphenomys in having a P4 with a weak buccal shelf, a more inflated protocone on upper molars, a more inflated and buccally positioned hypocone, and a smaller hypoconulid on lower molars.

MENG, JIN, NI, XIJUN, LI, CHUANKUI, BEARD, K. CHRISTOPHER, GEBO, DANIEL L., WANG, YUANQING, WANG, HONGJIANG (2007): New Material Of Alagomyidae (Mammalia, Glires) From The Late Paleocene Subeng Locality, Inner Mongolia. American Museum Novitates 3597 (1): 1-32, DOI: 10.1206/0003-0082(2007)3597[1:NMOAMG]2.0.CO;2, URL: http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1206%2F0003-0082(2007)3597%5B1%3ANMOAMG%5D2.0.CO%3B2

Neimengomys qii, new spesies HOLOTYPE: IVPP V14711.1, a right M1 (or M2) (fig. 13b). INCLUDED SPECIMENS: V 14711.2, left P4; V 14711.3���10, 8 M1s and/or M2s; V 14711.11���14, 4 M3S (or M2s); V 14712.1, right p4; V 14712.2, right m1; V 14712.3���5, 14712.3���5, 3 m3s (fig. 13). See table 5 for measurements. ETYMOLOGY: The trivial name is after Qi Tao (IVPP), who made the first discovery of Tribosphenomys specimens by screenwashing at Subeng in the 1980s. DIAGNOSIS: Same as for the genus. TYPE LOCALITY AND AGE: Subeng, about 25 km west of Erlian, Gashatan, Late Paleocene. COMPARATIVE DESCRIPTION: A P4 is identified for this species (fig. 13a). This tooth is smaller than those of T. minutus and transversely oval-shaped. The P4 buccal shelf is much narrower than that of T. minutus and is similar to that of A. inopinatus (Dashzeveg, 1990b). It differs from both Tribosphenomys and Alagomys in bearing a very small cuspule on the buccal shelf. Nine upper cheek teeth are considered to be either M1 or M2 (fig. 13b���j), which we cannot yet distinguish with confidence. These teeth have an oval shape in occlusal view. Compared to M1 of Tribosphenomys minutus these teeth are narrower and less symmetrical along the transverse axis, the protocone is more inflated, the hypocone is more inflated and buccally positioned, and the buccal shelf of the tooth is distinctly narrower. The width/ length ratio of these teeth is similar to that of M2 of T. minutus, but M2 of T. minutus is more triangular in occlusal view, the anterior edge of the tooth is much wider than its posterior counterpart, the protocone is anteroposteriorly more compressed, and the hypocone is usually absent. These teeth are also distinctive in size and morphology from upper molars of T. secundus (Lopatin and Averianov, 2004a). The molars of Neimengomys qii differ from M1 and/or M2 of Alagomys in having a hypocone and a more prominent buccal shelf. Among species of Alagomys, N. qii is more comparable with the North American A. russelli than the Asian A. inopinatus and A. oriensis. The Asian species are similar in have an anteroposteriorly compressed protocone, while A. russelli has an inflated protocone and a somewhat oval-shaped occlusal outline (Dawson and Beard, 1996: plate 1F). Subeng specimens differ from A. russelli in having a distinct buccal shelf on the upper molars, whereas the same structure is completely absent in A. russelli. In addition, the molar cusps of A. russelli are less isolated, the lophs are stronger, the protocone is more inflated, and the trigon basin is deeper. In addition, the basin and postcingulum between the protocone and metaconule are more prominent in Subeng specimens. Four specimens are identified as M3s (fig. 13k���n) of Neimengomys qii because of their small size and reduced metacone. Compared to M3 of T. minutus, the M3 of N. qii is also oval-shaped and has a more inflated, conical protocone. The M3 of N. qii is more transverse and cuspate than those of Alagomys (Dawson and Beard, 1996; Tong and Dawson, 1995). However, we cannot rule out the possibility that these teeth are M2. One p4 is identified as N. qii because of its smaller size and unique morphology. Unlike those referred to T. minutus, the p4 (fig. 13o) has a narrow trigonid consisting of two closely appressed cusps. In contrast, the talonid is wider than the trigonid and formed by two transverse, ridgelike cuspids. The p4 is similar in morphology to that of T. secundus (Lopatin and Averianov, 2004a), but differs in being much smaller. The m1 of N. qii (fig. 13p) has a narrower trigonid than those of T. minutus and a hypoconulid that is aligned with the entoconid as a ridge. Three m3s are referred to T. qii (fig. 13q���s). The hypoconulid on these m3s is more transverse than conical, differing from those referred to T. minutus. The trigonid basin of the lower molar is somewhat restricted, similar to that of T. minutus. In contrast, the trigonid basin in Alagomys is more open. Although the material is fragmentary, the morphologies of these teeth show that they must be from a previously unknown taxon. Based on these specimens, we propose a new genus and species of alagomyid., Published as part of MENG, JIN, NI, XIJUN, LI, CHUANKUI, BEARD, K. CHRISTOPHER, GEBO, DANIEL L., WANG, YUANQING & WANG, HONGJIANG, 2007, New Material Of Alagomyidae (Mammalia, Glires) From The Late Paleocene Subeng Locality, Inner Mongolia, pp. 1-32 in American Museum Novitates 3597 (1) on pages 16-21, DOI: 10.1206/0003-0082(2007)3597[1:NMOAMG]2.0.CO;2, http://zenodo.org/record/4735366, {"references":["Dashzeveg, D. 1990 b. New trends in adaptive radiation of early Tertiary rodents (Rodentia, Mammalia). Acta Zoologica Cracoviensia 33: 37 - 44.","Lopatin, A. V., and A. O. Averianov. 2004 a. A new species of Tribosphenomys (Mammalia: Rodentiaformes) from the Paleocene of Mongolia. In S. G. Lucas, K. E. Zeigler and P. E. Kondrashov (editors), Paleogene mammals. New Mexico Museum of Natural History and Science Bulletin 26: 169 - 175.","Meng, J., and A. R. Wyss. 2001. The morphology of Tribosphenomys (Rodentiaformes, Mammalia): phylogenetic implications for basal glires. Journal of Mammalian Evolution 8 (1): 1 - 71.","Lopatin, A. V., and A. O. Averianov. 2004 b. The earliest rodents of the genus Tribosphenomys from the Paleocene of Central Asia. Doklady Biological Sciences 397: 336 - 337.","Dawson, M. R., and C. K. Beard. 1996. New Late Paleocene rodents (Mammalia) from Big Multi Quarry, Washakie Basin, Wyoming. Palaeovertebrata 25: 301 - 321.","Tong, Y. - S., and M. R. Dawson. 1995. Early Eocene rodents (Mammalia) from Shangdong Province, China. Annals of Carnegie Museum 64: 51 - 63.","Meng, J., C. - K. Li, X. - J. Ni, Y. - Q. Wang, and K. C. Beard. 2007. A new Eocene rodent from the lower Arshanto Formation in the Nuhetingboerhe (Camp Margetts) area, Inner Mongolia. American Museum Novitates 3569: 1 - 18.","Li, C. - K., J. - J. Zheng, and S. - Y. Ting. 1989. The skull of Cocomys lingchaensis, an Early Eocene Ctenodactyloid rodent of Asia. In C. C. Black and M. R. Dawson (editors), Papers on fossil rodents in honour of Albert Elmer Wood: Natural History Museum of Los Angeles County Science Series, 33: 179 - 192.","Averianov, A. O. 1996. Early Eocene Rodentia of Kyrgyzstan. Bulletin du Museum National d'Histoire Naturelle 18: 629 - 662.","Wang, B. - Y., and M. R. Dawson. 1994. A primitive Cricetid (Mammalia: Rodentia) from the Middle Eocene of Jiangsu Province, China. Annals of Carnegie Museum, 63: 239 - 256."]}

Neimengomys, new genus TYPE SPECIES: Neimengomys qii, new species ETYMOLOGY: Nei-Meng is Chinese (in pinyin) for ������Inner Mongolia������; mys is Greek for ������mouse������, in analogy with Alagomys and Tribosphenomys. DIAGNOSIS: Differs from Alagomys but resembles Tribosphenomys in having a buccal shelf and a hypocone on upper molars, a more transverse M3 with conical cusps, and a narrower talonid basin. Differs from Tribosphenomys in having a P4 with a weak buccal shelf, a more inflated protocone on upper molars, a more inflated and buccally positioned hypocone, and a smaller hypoconulid on lower molars., Published as part of MENG, JIN, NI, XIJUN, LI, CHUANKUI, BEARD, K. CHRISTOPHER, GEBO, DANIEL L., WANG, YUANQING & WANG, HONGJIANG, 2007, New Material Of Alagomyidae (Mammalia, Glires) From The Late Paleocene Subeng Locality, Inner Mongolia, pp. 1-32 in American Museum Novitates 3597 (1) on page 15, DOI: 10.1206/0003-0082(2007)3597[1:NMOAMG]2.0.CO;2, http://zenodo.org/record/4735366

NI, XIJUN, BEARD, K. CHRISTOPHER, MENG, JIN, WANG, YUANQING, GEBO, DANIEL L. (2007): Discovery of the First Early Cenozoic Euprimate (Mammalia) from Inner Mongolia. American Museum Novitates 3571 (1): 1-12, DOI: 10.1206/0003-0082(2007)528[1:DOTFEC]2.0.CO;2, URL: http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1206%2F0003-0082(2007)528%5B1%3ADOTFEC%5D2.0.CO%3B2