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DOBUNNODON GEN. NOV. Z o o b a n k r e g i s t r a t i o n: L S I D u r n:l s i d:z o o b a n k. org:act: 46E0C61F-64A3-4B30-8780-AB634A882043. Type species: ‘ Borealestes ’ mussettae Sigogneau Russell, 2003. Etymology: The genus is derived from one of the Iron Age Celtic tribes, the Dobunni, that occupied the region around Kirtlington where the holotype was discovered, and the Greek δόντι, tooth.

BOREALESTES CUILLINENSIS SP. NOV. Zoobank registration: LSID urn:lsid:zoobank. org:act: E2EDCA4C-B0F7-46F1-AB7A-118C3575BE69. Holotype: NMS G.2020.4.1.1, a partial skull and postcranial remains (Fig. 3). Stratigraphic provenance: Kilmaluag Formation, Late Bathonian, Middle Jurassic (Retrocostatum Zone: Barron et al., 2012). Type locality: Cladach a’ Ghlinne, Strathaird Peninsula, Isle of Skye, Scotland UK (Fig. 1). Referred material: From the Kilmaluag Formation, Isle of Skye: Partial left dentary BRSUG 20571; NMS G.2018.27.1, fragment of right dentary in matrix. From the Forest Marble Formation of Kirtlington, Oxfordshire: NHMUK PV M46394, NHMUK PV M46448, NHMUK PV M46580 and NHMUK PV M46871, all upper molars. NHMUK PV M46316, NHMUK PV M46396 and, possibly, NHMUK PV M46607 (uncertain), all upper molars. Etymology: Species named for the Cuillinensis, a mountain range on the Isle of Skye, Scotland, which overlooks the holotype locality; the skyline of the mountain range resembles the cusps and ridges of the teeth. Differential diagnosis: Borealestes cuillinensis resembles Borealestes serendipitus in most features of the upper molars, but differs in having a more rounded cusp A, so that there is no anterior crest and no anterolabial crest on cusp A (Figs 5a and b, 6). Borealestes cuillinensis has a shorter anterolingual crest on cusp X than B. serendipitus, with a cuspule on the crest. Cusp Z is reduced compared to B. serendipitus. The anterior fovea is less distinct than in B. serendipitus. In the lower dentition, B. cuillinensis is almost indistinguishable from that of B. serendipitus, except for having slightly more pointed molar cusps. The lappets of the dentary do not enclose the cartilage of the Meckel’s sulcus of B. cuillinensis, unlike in B. serendipitus, and the mandibular symphysis is less distinct in B. cuillinensis than in B. serendipitus (Fig. 7). Description: The holotype NMS G.2020.4.1.1 is a partial skeleton that, following preparation for high-resolution CT scanning, is contained within a series of small blocks of blue-grey micritic limestone between ~2 and 5 cm length. The dentaries and some skull elements are partially visible on the surface, and within the rocks are the skull, vertebrae, scapulacoracoid, humerus, radii, ribs and pes and manus elements. We infer that NMS G.2020.4.1.1 is an adult individual, as the last (ultimate) lower molar is positioned directly in front the coronoid process, as in adult specimens of Docodon victor (Schultz et al., 2017).

DOBUNNODON MUSSETTAE (SIGOGNEAU- RUSSELL, 2003) COMB. NOV. BOREALESTES MUSSETTI SIGOGNEAU- RUSSELL, 2003 BOREALESTES MUSSETTAE AVERIANOV, 2004 (EMENDED GENDER) Holotype: NHMUK PV M46495, a right lower molar (Fig. 5C 1���4). Stratigraphic provenance: Forest Marble Formation, Late Bathonian, Middle Jurassic (Retrocostatum Zone: Barron et al., 2012). Ty p e l o c a l i t y: K i r t l i n g t o n C e m e n t Q u a r r y, Oxfordshire, UK. Referred material: From the Forest Marble Formation of Kirtlington, Oxfordshire: NHMUK PV M46224, NHMUK PV M46239, NHMUK PV M46001, NHMUK PV M46066, NHMUK PV M46836, NHMUK PV M46319, NHMUK PV M46809 and NHMUK PV M46835, all lower molars. From the Forest Marble Formation of Watton Cliff, Dorset: NHMUK PV M46001, lower molar. Etymology: The species name was given in honour of Dr Frances Mussett for her ���major participation in the accumulation of the Kirtlington fauna��� (Sigogneau-Russell, 2003). Differential diagnosis: Dobunnodon mussettae resembles other docodontans in that it possesses an anterior ���pseudotalonid basin��� on the lower molars, formed by cusps a, b, and g, has cusps b���a���c in a triangular arrangement, the lower molars are elongated anteroposteriorly, with labial row of higher cusps arranged in anteroposterior alignment with largest cusp a, and it has a lingual row of smaller cusps with distinctive anterior cusp g and larger posterior cusp c. The lower molar of Dobunnodon is unlike most docodontans, but is similar to Tashkumyrodon in being mediolaterally compressed. It resembles most docodontans, but differs from Borealestes in that the a���g crest is present on both cusp g and cusp a, and in having a strong a���d crest on cusp a (Fig. 5c). Cusp g is slightly more developed, and cusps c and g are placed further apart anteroposteriorly, than in Borealestes. Unlike Simpsonodon, Agilodocodon and Docodon, but like most other docodontans, Dobunnodon lacks creases and pits��� ���ornamentation��� on the teeth. Dobunnodon has an anterior lingual cingulid that passes below cusp g to midway along the molar anteroposteriorly. The df cusp is more developed in Dobunnodon than in Borealestes and is distinct from the d cusp. Cusp e is positioned in alignment with the anteroposterior axis of the molar, whereas cusp e is lingual of the anteroposterior axis on molars of Borealestes. The upper molars are not yet known for this taxon. Description: The holotype NHMUK PV M46495, is a single, right, lower molar, lacking a root and broken at the base of cusp a (reconstructed for Fig. 5C), previously described by Sigogneau-Russell (2003) and Panciroli et al. (2019)., Published as part of Panciroli, Elsa, Benson, Roger B. J., Fernandez, Vincent, Butler, Richard J., Fraser, Nicholas C., Luo, Zhe-Xi & Walsh, Stig, 2021, New species of mammaliaform and the cranium of Borealestes (Mammaliformes: Docodonta) from the Middle Jurassic of the British Isles, pp. 1323-1362 in Zoological Journal of the Linnean Society 192 (4) on page 1333, DOI: 10.1093/zoolinnean/zlaa144, http://zenodo.org/record/5856067, {"references":["Averianov AO. 2004. Interpretation of the Early Cretaceous mammal Peraiocynodon (Docodonta) and taxonomy of some British Mesozoic docodonts. Russian Journal of Theriology 3: 1 - 4.","Barron AJM, Lott GK, Riding JB. 2012. Stratigraphic framework for the Middle Jurassic Strata of Great Britain and the adjoining continental shelf: research report RR / 11 / 06. Keyworth: British Geological Survey, 177.","Sigogneau-Russell D. 2003. Docodonts from the British Mesozoic. Acta Palaeontologica Polonica 48: 357 - 374.","Panciroli E, Benson RBJ, Luo Z-X. 2019. The mandible and dentition of Borealestes serendipitus (Docodonta) from the Middle Jurassic of Skye, Scotland. Journal of Vertebrate Paleontology 39: e 1621884."]}

BOREALESTES SERENDIPITUS WALDMAN & SAVAGE, 1972 Holotype: Partial left dentary, BRSUG 20570. Stratigraphic provenance: Kilmaluag Formation, Late Bathonian, Middle Jurassic (Retrocostatum Zone: Barron et al., 2012). Type locality: Just south of Cladach a’ Ghlinne, Strathaird Peninsula, Isle of Skye, Scotland UK (Fig. 1). Referred material: From the Kilmaluag Formation, Isle of Skye: NMS G.1992.47.121.1, partial skeleton. Etymology: Species name from noun serendipity, defined as the faculty of making happy and unexpected discoveries by accident. Differential diagnosis: Dental formula 4.1.?5.4/?4.1.5.5(6). Borealestes serendipitus differs from Borealestes cuillinensis, the only other species in the genus, in having distinct anterolabial and anterolingual crests between cusps A and X in the upper molars, and in that cusp Z is reduced (Figs 5a and b, 6). The anterior fovea is more distinct than in B. cuillinensis. The lower molar cusps are slightly less dorsoventrally tall in B. serendipitus than in B. cuillinensis. The lappets of the dentary enclose the cartilage of the Meckel’s sulcus of B. serendipitus from the point ventral to the m3–m 4 in adult specimens, leaving a faint line running anteriorly, unlike in B. cuillinensis where it remains an open sulcus in the adult (Fig. 7). The mandibular symphysis of B. serendipitus remains distinct until ventral to the p3– p4, whereas it is much less distinct in B. cuillinensis. Description: The holotype BRSUG 20570 is a partial left dentary, removed from matrix, with nine teeth in their alveoli (one only comprising roots). It measures 11 mm in length.

BOREALESTES WALDMAN & SAVAGE, 1972 Type species: Borealestes serendipitus Waldman & Savage, 1972. Revised differential diagnosis: Dental formula 4.1.?5.4/4.1.5.5(6). As in other docodontans: possesses an anterior ���pseudotalonid basin��� formed by cusps a, b and g; retains plesiomorphic mammaliaform trait of attachment of postdentary elements to the dentary; has an eflected angular process (sensu Simpson, 1929; also see: Schultz et al., 2017: figs 2, 3); enlarged medial ridge protuberance (sensu Schultz et al., 2017); and enlarged and pointed upper and lower canines that are twin-rooted. The lower molars of Borealestes are: elongated anteroposteriorly, with labial row of higher cusps arranged in anteroposterior alignment with largest cusp a, and lingual row of smaller cusps with distinctive anterior cusp g and larger posterior cusp c; lower molars have cusps b���a���c in a triangular arrangement. The a���g crest on cusp a is absent (present to variable extent on cusp g) and the a���d crest on cusp a is also absent (but a labially oriented a���d crest is present on cusp d). Borealestes has a distinctive a���c crest. Upper molars of Borealestes: buccolingually wide and anteroposteriorly short; ���figure 8��� shape, with anteroposteriorly constricted waist; two main buccal cusps, A and C, plus a small cusp B in the buccomesial corner; lingual half of the upper molar has main anterior lingual cusp X; cusp X larger and more prominent than smaller posterior lingual cusp Y; labial cusps connected by a ridge/ ridges anteroposteriorly; transverse ridge extends between the main anterior labial cusp A and the main lingual cusp X. In the lower molars, Borealestes most closely resembles docodontans Krusatodon, Castorocauda and Haldanodon in sharing a larger cusp c than cusp g. It resembles Castorocauda and possibly also Itatodon in having a slightly recurved cusp c. Borealestes is similar to Castorocauda and Docodon in possessing an anterior ���cingulid��� incorporating cusp e, and cusp e is anteriorly projecting and forms part of the d���df���e interlock with the neighbouring molar, as in Krusatodon and Simpsonodon. Borealestes has a distinct lingual cingulid in the premolars, and a posterior labial cingulid, as seen in most other docodontans. Unlike Simpsonodon, Agilodocodon and Docodon, but like most other docodontans, Borealestes does not have dense creases and pits or other ornamentation on molar enamel surfaces. Borealestes differs from Dobunnodon mussettae in having more elevated b���g crest and c���d crest, and the more lingually positioned cusp e. Borealestes differs from all other docodontans, except Docodon, in having an anterior fovea (sensu Panciroli et al., 2019: fig 1B3) on the upper molars: a concave area anterior to the anterolingual crest. Borealestes differs from Docodon in having the anterior fovea positioned at the anteroposteriorly constricted waist of the upper molars. Borealestes differs from Krusatodon, Agilodocodon, Simpsonodon, Docodon and Haldanodon in having a transversely expanded and anteroposteriorly slightly compressed lingual wing of the upper molar, similar to Docofossor and Dsungarodon. Borealestes resembles Docofossor and Dsungarodon in having more reduced cusps Y and Z on the upper molars, and a larger cusp X. Referred specimens: Specimens referred to Borealestes sp. but not to species level from the Kilmaluag Formation, Isle of Skye: BRSUG 29007, fragment of right dentary; BRSUG 29008, three fragmentary molars in matrix., Published as part of Panciroli, Elsa, Benson, Roger B. J., Fernandez, Vincent, Butler, Richard J., Fraser, Nicholas C., Luo, Zhe-Xi & Walsh, Stig, 2021, New species of mammaliaform and the cranium of Borealestes (Mammaliformes: Docodonta) from the Middle Jurassic of the British Isles, pp. 1323-1362 in Zoological Journal of the Linnean Society 192 (4) on pages 1329-1331, DOI: 10.1093/zoolinnean/zlaa144, http://zenodo.org/record/5856067, {"references":["Waldman M, Savage RJG. 1972. The first Jurassic mammal from Scotland. Journal of the Geological Society of London 128: 119 - 125.","Simpson GG. 1929. American Mesozoic Mammalia. Memoirs of the Peabody Museum of Yale University 3: 1 - 235.","Schultz JA, Bhullar BAS, Luo Z-X. 2017. Re-examination of the Jurassic mammaliaform Docodon victor by computed tomography and occlusal functional analysis. Journal of Mammalian Evolution 26: 9 - 38.","Panciroli E, Benson RBJ, Luo Z-X. 2019. The mandible and dentition of Borealestes serendipitus (Docodonta) from the Middle Jurassic of Skye, Scotland. Journal of Vertebrate Paleontology 39: e 1621884."]}

Tritylodontidae was a successful advanced cynodont clade with a close relationship to mammals, but falling outside the clade Mammaliaformes.Stereognathus ooliticuswas the first tritylodontid to be named and described in 1854, but since then no comprehensive description for this species has been produced. A second species,S. hebridicus, was named in 1972 and diagnosed based solely on size difference, being larger than theS. ooliticusholotype. We reexamined all postcanine tooth material attributed to the genusStereognathusto test the species diagnosis and identify diagnostic morphological characters for this genus. We find no statistical difference in size distribution betweenS. ooliticusandS. hebridicuspostcanine specimens. Specimens previously attributed to the different species fall along an ontogenetic spectrum of size, with no clear clustering. Morphologically, we affirm many previously described features forStereognathusand identify new morphological features in upper and lower postcanines. We find no morphological features to distinguish these two species, and therefore we synonymizeS. hebridicusunderS. ooliticus. We reevaluate the scoring ofS. ooliticusin previous phylogenetic analyses, generating a new tree using rescoredStereognathuscharacters. Finally, we suggest that similar reevaluations and redescriptions of other poorly described tritylodontid material are necessary to further clarify relationships among Tritylodontidae and the evolution of characters in derived genera such asStereognathus.