Micro-computed tomography reveals a diversity of Peramuran mammals from the Purbeck Group (Berriasian) of England



    1. Department of Zoology and the Sam Noble Oklahoma Museum of Natural History, University of Oklahoma, Norman, OK 73072, USA; e-mail: Davis-B@mssu.edu
    2. Current address: Department of Biology and Environmental Health, Missouri Southern State University, Joplin, MO 64801, USA
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Abstract:  The known sample of the important pretribosphenic mammal Peramus tenuirostris, housed in the Natural History Museum (London, UK), was imaged using micro-computed tomography (CT). Substantial morphological diversity was discovered, prompting establishment (and resurrection) of additional taxa from within the existing hypodigm of Peramus tenuirostris: Peramus dubius comb. nov., Kouriogenys minor gen. nov. and Peramuroides tenuiscus gen. et sp. nov. The Peramura are revised; this group is restricted to taxa with clear evidence of a fully functional upper molar embrasure for the dominant lower molar talonid cusp (hypoconid), either through development of wear facet 4 or through differentiation of a distinct hypoconulid. The Peramura are the most likely sister taxon to the Tribosphenida (including living marsupials and placentals) and represent a distinct molar morphotype, transitional between primitive lineages characterized by dominant orthal shear (e.g. dryolestoids) and those with modern, multi-functional tribospheny. A very large masseteric foramen is identified in peramurans, but this feature appears to be autapomorphic and of uncertain function.