New species of mammaliaform and the cranium of Borealestes (Mammaliformes: Docodonta) from the Middle Jurassic of the British Isles Author Panciroli, Elsa Author Benson, Roger B. J. Author Fernandez, Vincent Author Butler, Richard J. Author Fraser, Nicholas C. Author Luo, Zhe-Xi Author Walsh, Stig text Zoological Journal of the Linnean Society 2021 2021-01-27 192 4 1323 1362 http://dx.doi.org/10.1093/zoolinnean/zlaa144 journal article 2567 10.1093/zoolinnean/zlaa144 eee94db3-df5c-46ee-92a7-fb23e558f663 0024-4082 5856067 320C0FA6-04F0-4D5C-93BF-D14160AFBB4F 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.