They lived in pairs, in the small burrows of the Triassic period. They could create their own burrows, but they could also penetrate in holes already made. They were the size of a small dog. Some creatures like Coelophysis, small dinosaurs, were potential menaces to the baby Thrinaxodon, and the adults must be always watching their young.
Walking with DinosaursEdit
Thrinaxodon appeared in the first episode of Walking with Dinosaurs, New Blood. A pair of them are found by a group of Coelophysis, and drive them away the first time but the dinosaurs don't give up easily and the Thrinaxodon find themselves forced to eat their own young so the coelophysis do not have any more food there and abandon the burrow. However, they later have a new cluch of eggs.
In fact, Thrinaxodon didn't lived 220 millions years ago, it lived between 248 and 245 million years BC