Cotylorhynchus

Cotylorhynchus is an extinct genus of herbivorous caseid synapsids that lived during the late Lower Permian (Kungurian) and possibly the early Middle Permian (Roadian) in what is now the states of Texas and Oklahoma in the United States. The large number of specimens found make it the best-known caseid. Like all large herbivorous caseids, Cotylorhynchus had a short snout sloping forward and very large external nares. The head was very small compared to the size of the body, which was massive, barrel-shaped, and ended with a long tail. The barrel-shaped body must have housed large intestines, suggesting that the animal had to feed on a large quantity of plants of low nutritional value. The limbs were short and robust. The hands and feet had short, broad fingers with powerful claws. Caseids are generally considered to be terrestrial, though a semi-aquatic lifestyle has been proposed by some authors. The genus Cotylorhynchus is represented by three species, the largest of which could reach more than 6 metres (20 feet) in length. However, a study published in 2022 suggests that the genus may be paraphyletic, with two of the three species possibly belonging to separate genera.