DEVELOPMENT OF EARLY PELYCOSAURS
The synapsid group of reptiles are classified by the fact that the holes in the skull behind the eyes were fused into a single opening. This big opening provided a very strong anchoring area for the jaw muscles and led to powerful and widely-opening jaws in some of the examples. The main evolutionary line of these became the mammal-like reptiles and ultimately the mammals. Realistic Dinosaur Costume
The earliest representatives were the pelycosaurs. The name “pelycosaur” literally means “basin lizards”, and is a reference to the arrangement of the bones in the hip. which produced a basin-like structure. Dinosaur Playground Equipment
The oldest pelycosaur was Protoclepsydrops from the Carboniferous. It was also the oldest-known synapsid, from the tree-stump Icxality of Joggins. Nova Scotia. The earliest pelycosaurs were small, lizard-like animals , but they evolved into respectably-sized animals, some with spectacular sails on their backs.
We can see the transition from the sail-less Sphenacodon to a big-sailed form such as Dimetrodon through an intermediate type. Ctenospondylus. which was identical to these two in body arrangement, but had a sail that was only half the size of that of Dimetrodon. Another form, Secodontosaurus. was similar to Dimetrodon but had a much flatter head. The pelycosaurs did not survive the middle Permian.