Pelycosaur | fossil tetrapod order | Britannica

…are divided into two orders: pelycosaurs and therapsids. They show a remarkably complete transition in skeletal features from typical early reptiles (Early Permian Epoch) into true mammals (in the Middle and Late Triassic epochs) through a fossil record lasting about 80 million years. The Early Permian pelycosaurs included carnivores and…

…terrestrial groups, such as the pelycosaurs (fin-backed reptiles), Moschops (a massive mammal-like reptile), and numerous families of insects also met their demise. In addition, a number of groups (such as sharks, bony fishes, brachiopods, bryozoans,