Typically, they are considered synapsids that evolved from an "Archaeothyris"-like synapsid in the Late Carboniferous. "Dimetrodon" was a quadrupedal, sail-backed synapsid. Most of the earlier anapsid/synapsid megafauna disappeared, being replaced by the archosauromorph diapsids. By the mid-Triassic, there were many synapsid species that looked like mammals. When only cranial or skull features were included, Caseasauria remained the most basal synapsid clade. Eothyris is a genus of extinct synapsid in the family Eothyrididae from the early Permian. One synapsid group, the pelycosaurs, included the largest and fiercest animals of the early Permian. Because more advanced synapsid group therapsida evolved directly from the pelycosaurs, the pelycosaurs are paraphyletic. These included the earliest sauropsid reptiles ("Hylonomus"), and the earliest known synapsid ("Archaeothyris"). Paleontologist E. C. Case named a new species of sail-backed synapsid, "Theropleura grandis", in 1907. The tail was unusually long for a synapsid. "Moschops" were heavy set dinocephalian synapsid, that were roughly in length. This may also explain why there is no fossil evidence for synapsid eggs to date. It has the longest skull of any early synapsid, reaching up to in one specimen.