Friday, March 11, 2016

Mupashi migrator: a new Karenitid Therocephalian From Upper Permian Zambia

The first karenitid (Therapsida, Therocephalia) from the upper Permian of Gondwana and the biogeography of Permo-Triassic therocephalians


Huttenlocker et al


Therocephalians were an ecologically diverse group of therapsids whose long stratigraphic record and widespread distribution during Permian and Triassic times make them important for understanding biogeographic patterns during a major faunal transition. Here, we describe a new therocephalian, Mupashi migrator gen. et sp. nov., from the upper Madumabisa Mudstone Formation (upper Permian) of Zambia's Luangwa Basin. The specimen has a long snout with a maxilla–vomerine contact on the hard palate, a high antecanine tooth count and numerous postcanines, and a conspicuous boss on the dentary angle whose structure is identical to that of the Russian baurioid Karenites. Additional endocranial anatomy, including palatal and braincase features, are revealed by high-resolution X-ray computed tomography and described in detail in light of the growing availability of tomographic data for therapsids. A phylogenetic analysis of 56 therapsid taxa and 136 cranial and postcranial characters recovers Mupashi as the sister taxon to Karenites, placing the pair between basal ictidosuchid-grade baurioids and the later Triassic bauriamorphs. Parsimony optimizations of geographic occurrences are ambiguous regarding the origination centers of therocephalian subclades. However, the patterns are suggestive of either (1) rapid, early dispersal events of Eutherocephalia and its major subgroups from a Laurasian center during the early–late Permian or, more likely, (2) within-province diversifications with occasional dispersal events occurring between provinces. Regardless, these associations strengthen the hypothesis that unknown but effective dispersal routes to high latitudes were available to therapsids and other tetrapods at least until early–late Permian times.

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