Thrinaxodon was a small meat-eating cynodont that lived on the Late Triassic 250 million years ago. It is characterized by having dog-like canine, molar, and incisor teeth. Thrinaxodon was able to breathe while eating, a characteristic that most reptiles did not yet have. It is suspected that Thrinaxodon may have been covered in hair, suggesting the climate consisted of hot days and cold nights.

According to its powerful front legs, it may have lived in burrows only coming out at night to hunt for food. Litter habits range from from three to five pups. If faced with starvation, they would kill and eat their own young. Males may have used scent traces to mark their territory. When another male stumbles across another's territory, it is a fight to the death.

Judging by their thick necks they could hold large vocal cords to create a low-pitch growl to warn off predators.