Lystrosaurus

Lystrosaurus (; 'shovel lizard'; from Ancient Greekλίστρονlístron 'tool for leveling or smoothing, shovel, spade, hoe') is an extinct genus of herbivorousdicynodonttherapsids from the late Permian and Early Triassicepochs (around 248 million years ago). It had a widespread distribution across Pangaea, with fossils having been found in what is now Antarctica, India, China, Mongolia, European Russia, South Africa, and possibly Australia and Mozambique. Four to six species are currently recognized, but from the 1930s to 1970s the number of species was thought to be much higher.

As a dicynodont, Lystrosaurus had only two teeth (a pair of tusk-like canines), and is thought to have had a horny beak that was used for biting off pieces of vegetation. It was a heavily built, herbivorous animal. The structure of its shoulders and hip joints suggests that it moved with a semi-sprawling gait. Its forelimbs were even more robust than its hindlimbs, and it is thought to have been a powerful digger that nested in burrows.

Lystrosaurus survived the Permian-Triassic extinction event (Earth's most severe) 252 million years ago and thrived in the immediate aftermath; its fossils are, by far, the most common terrestrial vertebrate fossils in Early Triassic beds around the world, such as in the Lystrosaurus Assemblage Zone in South Africa. Researchers have offered various hypotheses for why it survived the extinction event and thrived in the early Triassic.