Proterogyrinus was an anthracosaur, a large group of reptilian reptiliomorphs. It is likely that the first reptiles, such as Petrolacosaurus, evolved from reptilomorphs. Like other reptiliomorphs, such as Seymouria, Proterogyrinus could venture further away from water than most amphibians.
Its name is Greek for "early wanderer" or "earlier tadpole".
During the Late Carboniferous period (326 - 318 million years ago), the amphibians were an exciting and diverse group of animals that had come to dominate the waterlogged forest world. They also were evolving into reptiles, which produced the unique and interesting reptiliomorphs.
Proterogyrinus was one of the largest of its reigion, and was perfectly adapted for life in the swamps. It was a top predator that hunted both on land and in the water. Its powerful jaws had sharp teeth that could handle animals that were quite large, such as fish, large arthropods, and other reptiles and amphibians.
Proterogyrinus was similar in shape to other prehistoric amphibians, and reptiliomorphs, such as Crassigyrinus and Eryops. It was about two and a half meters (7-8 feet) long, similar in size to the biggest modern lizards.