Romeriida

Romeriida is a clade of reptiles that consists of diapsids and the extinct protorothyridid genus "Paleothyris", if not the entire family Protorothyrididae. It is phylogenetically defined by Laurin & Reisz (1995) as the last common ancestor of "Paleothyris" and diapsids, and all its descendants. It is named after Alfred Romer, a prominent vertebrate paleontologist of the twentieth century.
Protorothyridids were once placed in the family Romeriidae along with the captorhinid "Romeria". Because "Romeria" is now considered to be a captorhinid, and Captorhinidae is placed outside Romeriida, the genus is excluded from the clade. Protorothyridids were once the collective term for several romeriid genera of uncertain classification. However, more recent studies have proposed that Protorothyrididae is a paraphyletic taxon. Therefore, it is possible that many protorothyridids do not lie within the clade Romeriida.
Several synapomorphies characterize the romeriids. These include the separation of the tabular bone from the opisthotic bone, ventrally keeled anterior pleurocentra, long and slender carpi and tarsi, and overlapping metapodials.
Below is a cladogram showing the placement of Romeriida within Amniota, modified from Hill, 2005:
Cladogram after Müller & Reisz, 2006:
 Polyphyletic Protorothyrididae