Evolution of the Dinosaurs

Dinosaur Ancestors

What were some of the earliest known reptiles?

Two of the earliest known reptiles, the Hylonomus and Paleothyris, both descended from amphibians during the Middle Carboniferous period of the Paleozoic era. The best evidence of the change from amphibian to reptile was the early reptiles’ high skulls—evidence of additional jaw muscles—and thicker egg shells. The Hylonomus still claims the prize (so far) as the oldest-known reptile and lived about 315 million years ago. The Paleothyris evolved about 300 million years ago. The fossils of both these reptiles were found near Nova Scotia, Canada, in ancient tree stumps. Apparently, the animals fell into tree stumps in pursuit of insects or worms. There they were trapped and eventually died.


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