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 MORPHOLOGY OF BOREALESTES SERENDIPITUS AND BOREALESTES CUILLINENSIS NMS G.1992.47.121.1 comprises a partial skeleton of Borealestes serendipitus on a block of blue-grey limestone. The block measures approximately 183 mm in length, 105 mm in width and between 148 and 340 mm in thickness. The surface of NMS G.1992.47.121.1 is undulating, with several hairline cracks visible in the prepared upper surface, also visible in synchrotron CT data. Skeletal elements are scattered on the surface of the block, including the palate and elements of the skull ( Figs 2 , 8 ). Synchrotron CT data revealed vertebrae, ribs, radius, partial humerus, ilium, femur and manus and pes elements within the block (unpubl. data EP). The surface bones sit on ‘platforms’ of rock, the result of acid and mechanical preparation, whereby the surrounding rock was removed. At least seven such platforms no longer contain fossil material, and likely indicate the original positions of bones that have been removed or detached during handling, such as the petrosal NMS G.1992.47.121.2 ( Panciroli et al. , 2018a ) and the dentary NMS G.1992.47.121.3 ( Panciroli et al. , 2019 ). NMS G.2020.4.1.1 comprises a partial skeleton of Borealestes cuillinensis contained within a series of small blocks of blue-grey limestone between ~2 and 5 cm long ( Fig. 3 ). The skull is present between two of these blocks, which were broken apart across a natural crack in the limestone. The left dentary is visible on the surface, along with the right squamosal and part of the occipital condyles. The rest of the skull is contained within the rock and visible through X-ray µCT ( Figs. 3 , 9 ).