Chasmatosaurs are the earliest ancestors of crocodiles and alligators.
— Allen, describing Chasmatosaurus

Chasmotosaurs was among the earliest ancestors of the modern crocodilians (alligators and crocodiles). They walked like dinosaurs, and they brought down their prey like crocodiles, but they couldn't do the death roll. They were also longer than some of the modern crocodiles are.

They were dangerous riverside hunters, and are well known from numerous fossils, indicating they were widly successful in the Early Triassic Period. Proterosuchus was one of the largest land reptiles during the Early Trassic Period. They were certainly the largest Archosaurs yet to evolve.Found during the Early Triassic. They lived with the first dinosaurs.



As basically primitive crocodilians, Chasmatosaurs lived during the Early Triassic Period 250-230 million years ago. The hunted Lystrosaurus. This animal died out when the first dinosaurs began to appear.


Chasmatosaurus was the largest land animal on earth during the early Triassic period in Antarctica, but in modern terms it was only a little bigger than a Komodo Dragon, over 3 meters long. These creatures are the earliest ancestors of crocodiles and alligators. Their strange over bite meant once they get their teeth into a victim, there was no chance of escape. They normally don’t gather in huge numbers.

With long jaws, powerful neck muscles, relatively long legs and a lengthy tail, it looked a bit like a primitive crocodile, and in fact did have a lifestyle that is broadly similar to the Nile crocodile of modern day Africa. The long, muscular tail of the chasmatosaurs was excellent for swimming, and could push it through the water at speed. However, the animal also had stout legs that enabled it to walk comfortably on land. Therapsids went on a decline.