The pelycosaurs were a varied family of synapsids. The were most dominate during the late carboniferous period and survived until the early permian period, a few even until the late permian period. Making them some of the first and largest mammals on earth.
Features
At least two species of pelycosaur, developed large sails that consisted of vertebral spines, these bony spikes would have been covered by skin and either worked as a form of heat regulation or even mating. These were the edaphosaurids and the sphenacodontids.
Fossil finds
Most of this family of fossils have been found in Europe and North America, however some of the later surviving forms have been found in Russia and South Africa. The most well known of these specicies are the; Dimetrodon, Sphenacodon, Edaphosaurus and the Ophiacodon. In 1940 Alfred Sherwood Romer and Llewellyn Price reviewed and detailed every known species of the time in a monograph. the group was reviewed in detail and every species known at the time described (and many illustrated) in an important monograph.
Not Dinosaurs
Pelycosauria as a term, is not often used in contemporary books because it includes therapsids, leaving Eupelycosauria a more appropriate term, designating most Pelycosaurs with Therapsida and mammals. One group the Caseasauria are the only branch of these reptiles that have no living descendents. The pelycosaurs appear to have been a group of reptiles that had direct ancestral links with the mammalia, having differentiated teeth and a developing hard palate, making them an important link to the rise of mammals.