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Mesozoic mammals from England



From: Ben Creisler
bcreisler@gmail.com


OK--not dinosaurs or birds--and based mainly on teeth--but theropods
and maybe pterosaurs ate these critters. Early mammals probably
competed with small or juvenile dinosaurs for insects and plants.


In the July 2012 issue of Palaeontology:


Brian M. Davis (2012)
Micro-computed tomography reveals a diversity of Peramuran mammals
from the Purbeck Group (Berriasian) of England.
Palaeontology 55(4):789–817
DOI: 10.1111/j.1475-4983.2012.01161.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2012.01161.x/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.