Lystrosaurus is a mammal like reptile from the early Triassic and the late Permian. It was a herbivore that lived in large herds. It was not a big animal but mainly the size of a small dog. Its defenses is its numbers and the tusks that grow from the sides of its mouth. Unlike latter mammals they had no relitive relationship with there kin so when one dies it simply move on like all reptiles. This therapod was the most common animal found during the Early Triassic. It was so common that its population made up 80 per cent of all life at the time, no other animal in history is as common than Lystrosaurus. It and a very few other creatures are survivors from the worst natural disaster that struck earth in its history.