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Traversodontidae is an advanced, large, plant-eating group of cynodonts that is part of the lineage Cynognathia, a line that includes the famous, fierce predator Cynognathus. Their postcanine teeth is modified and expanded in width for chewing plants. Traversodonts generally had relatively wide snouts, and the maxilla extends sidewards beyond the teeth. This may indicate the presence of useful bags known as cheeks. Such devices allow for food to be more thoroughly chewed. The skeletal feautures are almost mammalian than the earlier therapsids. Previous models had spines fitted with costal plates. These bits of bone overlapped with each other where the ribs met the back bone. These strengthed the spine, but what advantage that provided is unclear. Such features are much reduced in more basal traversodonts. The more advanced Traversodontids, (eg. Exaeretodon), did away with them entirely. This gives the spine a less clanky, more mammalian appearance. They may have laid eggs, like many other proto-mammals, and earlier synapsids. Traversodontids were abundant and successful during the world of the Middle and Late Triassic, and so some may have competed the early dinosaurs. They didn't quite made it to the Jurassic. The Traversodontids were one of the largest cynodonts (after Cynognathus). But as the Triassic age progressed, the Traversodontids were getting smaller. The last, large Traversodontid lived in the Late Triassic. At the same time, the Traversodontids were being pushed to extinction. By the Latest Triassic or Earliest Jurassic they became extinct. They probably suffered by the Triassic-Jurassic extinction event. Or they were probably outcompeted by their relatives, the Tritylodontids, which began to appear in the Late Triassic.
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