Eothyris

Eothyris is a genus of extinct synapsid in the family Eothyrididae from the early Permian. It was a carnivorous insectivorous animal, closely related to Oedaleops. Only the skull of Eothyris, first described in 1937, is known. It had a skull, and its total estimated length was . Eothyris is one of the most primitive synapsids known and is probably very similar to the common ancestor of all synapsids in many respects. The only known specimen of Eothyris was collected from the Artinskian-lower.

== Discovery and naming == Eothyris parkeyi was one of many new species of "pelycosaurs" discovered by Alfred Sherwood Romer as part of a series of paleontological expeditions for the Museum of Comparative Zoology (MCZ). The genoholotype (type specimen of a genus) and only known specimen of Eothyris is a complete skull and associated jaws, with the collection number MCZ 1161. This skull was collected about one mile west of the former Woodrum ranch-house, in Early Permian sediments of the Artinskian-lower Kungurian Belle Plains Formation, Wichita Group, south of Dundee, Texas, USA. in rocks which are about 275 million years old. The generic name is Greek for "dawn opening", likely in reference for its status as one of the most primitive known synapsids. The specific name refers to J.R. Parkey, of Mankins, Texas, a local landowner who assisted the MCZ field crew in collecting fossils on his property. Eothyris was briefly described by Romer in 1937, and given a more comprehensive description by Romer and Llewellyn Ivor Price in 1940.