Like other dicynodonts it had only two teeth (tusks) and a beak. It was a herbivore that walked on four legs. It was about 3 feet or 0.9 m long.
Because The Permian–Triassic (P–Tr) extinction event (also known as the Great Dying) had killed most of the other animals Lystrosaurus was the most common terrestrial vertebrate of the Early Triassic Period. For a while 95% of land vertebrates were Lystrosaurus.
The Lystrosaurus is a mix between a reptile and a mammal :)