Petrolacosaurus is an extinct genus of reptile that lived during the Carboniferous period, about 300 million years ago and one of the oldest known reptiles. It was a small, 40 cm long reptile that lived in what is now North America. Its teeth were slightly curved backwards, but its jaw muscles were poorly developed. Therefore, Petrolacosaurus is thought to be insectivorous. It lived on the forest floor of conifer forests and low vegetation, consisting of mainly ferns. Petrolacosaurus wasn’t an excellent climber and probably climbed in trees only when being chased.
Petrolacosaurus is the only species in its genus and family and was discovered in Kansas (USA) in 1932. It was fossilized in a layer of mud which also contained fossilized plants, insects and more. Therefore it is known in what environment Petrolacosaurus lived.
Peabody, F. E. (1952). Petrolacosaurus kansensis Lane, a Pennsylvanian reptile from Kansas.