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Brachyprosopus (dicynodont from Middle Permian of South Africa) redescribed



Ben Creisler
bcreisler@gmail.com


A new non-dino paper:



Kenneth D. Angielczyk, Bruce S. Rubidge, Michael O. Day & Florence Lin (2016)
A reevaluation of Brachyprosopus broomi and Chelydontops altidentalis,
dicynodonts (Therapsida, Anomodontia) from the middle Permian
Tapinocephalus Assemblage Zone of the Karoo Basin, South Africa.
Journal of Vertebrate Paleontology (advance online publication)
DOI:10.1080/02724634.2016.1078342
http: // www.tandfonline.com/doi/full/10.1080/02724634.2016.1078342


Brachyprosopus broomi was described in 1937 based on a specimen from
the Tapinocephalus Assemblage Zone (Karoo Basin, South Africa), but it
was largely overlooked by subsequent workers. We have identified
several new specimens that show that Brachyprosopus is a valid taxon.
An autapomorphy for the taxon is a curled lateral edge of the
squamosal that forms a lateral wall of the external adductor fossa.
Other important characters are absence of anterior median palatal
ridges; maxillary tooth rows bounded laterally by a shelf; unfused
vomers; raised margins of the interpterygoid vacuity; broad
intertemporal region; pineal boss; dentary tables; and a long, wide
posterior dentary sulcus that extends posterior to the dentary teeth.
Chelydontops altidentalis is a junior synonym of B. broomi. A
phylogenetic analysis places Brachyprosopus among basal dicynodonts,
not as a close relative of Endothiodon. It is noteworthy that some
characters, such as well-developed medial maxillary tooth rows and the
shape of the palatines, are shared by Brachyprosopus, Pristerodon,
Endothiodon, and Niassodon, hinting that a final resolution of
relationships among toothed dicynodonts remains to be achieved. Most
Brachyprosopus specimens are from the upper Abrahamskraal Formation
(Moordenaars and Karelskraal members). One specimen is from low in the
Koonap Formation, just above the lowermost maroon mudrocks of the
Beaufort Group, and an exact correlation between this level and the
strata of the Abrahamskraal Formation is uncertain. Therefore, it is
likely that the stratigraphic range of Brachyprosopus extends
throughout the Tapinocephalus zone and possibly down into the
Eodicynodon Assemblage Zone.