A New Late Permian Burnetiamorph From Zambia Confirms Exceptional Levels of Endemism in Burnetiamorpha (Therapsida: Biarmosuchia) and an Updated Paleoenvironmental Interpretation of the Upper Madumabisa Mudstone Formation

A new burnetiamorph therapsid, Isengops luangwensis , gen. et sp. nov., is described on the basis of a partial skull from upper Madumabisa Mudstone Formation Luangwa Basin northeastern Zambia. diagnosed by reduced palatal dentition, ridge-like palatine-pterygoid boss, exposure jugal that extends far anteriorly, tall trigonal pyramid-shaped supraorbital and recess along dorsal margin lateral temporal fenestra. The was deposited in rift basin with lithofacies characterized unchannelized flow, periods subaerial desiccation non-deposition, pedogenesis, can be biostratigraphically tied to Cistecephalus Assemblage Zone South Africa, suggesting Wuchiapingian age. second recognized Zambia part tetrapod assemblage remarkably similar others across southern Pangea during Wuchiapingian. revised cladistic analysis Biarmosuchia yielded over 500 most parsimonious trees generally reaffirm results previous analyses for burnetiamorphs: Lemurosaurus basal, Lobalopex are proximate burnetiid outgroups, Bullacephalus, Burnetia Mobaceras Niuksenitia Pachydectes burnetiines. Furthermore, Russian biarmosuchians scattered throughout tree do not form sister taxon relationships each other. Burnetiamorphs display wide disparity cranial adornments relatively speciose (13 species), especially when compared number specimens discovered date (?16 specimens). As has been suggested some other clades (e.g., ceratopsian dinosaurs), fossil record supports an inferred macroevolutionary relationship between adornment increased speciation rate.