Skeleton of Cotylorhynchus Romeri

  • Texas
  • Oklahoma
  • C. bransoni
  • C. hancocki
  • C. Romeri

Cotylorhynchus is a genus of Caseidae. It lived in the Permian in North America (Texas, Oklahoma) at the same time as many other synapsids also, among other things, Dimetrodon and Edaphosaurus. There are three known species: C. bransoni, C. and C. hancocki Romeri, with the latter the type species, so the species for the first described. Different parts of the skeleton of C. Romeri were found in Cleveland County in the U.S. state of Oklahoma. Cotylorhynchus was first described by J. Willis Stovall.


The length varies depending on the source of Cotylorhynchus 3-6 meters. The weight is estimated at 2 tons. The body is reminiscent of a ton. The skull was small. The blunt, iguana -like teeth indicate a herbivore, so on a herbivorous diet. Cotylorhynchus had relatively large compared to other claws Caseidae. Other features are the massive Scapulocoracoid, part of the shoulder girdle, the large end of the humerus ( upper arm bone), the thick bone of the forearm, as well as the broad, robust hand. The construction of the hands suggests that Cotylorhynchus could dig, presumably to dig roots from the soil.


Cotylorhynchus was a derived representative of Caseidae. The sister taxon forms Angelosaurus. Another close relative was Ennatosaurus. The Caseidae form the sister taxon of Eothyrididae whose only genera Eothyris and Oedaleops are; both families are summarized as Caseasauria. Below is a cladogram according Maddin et al. (2008):

Eothyris ( Eothyrididae )