Prolystrosaurus

Lystrosaurus Temporal range: Late Permian–Early Triassic, 255–250 Ma PreЄ Є O S D C P T J K Pg N ↓
Lystrosaurus hedini skeleton at the Museum of Paleontology, Tübingen
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Order:	Therapsida
Infraorder:	†Dicynodontia
Family:	†Lystrosauridae
Genus:	†Lystrosaurus Cope, 1870
Species
List L. murrayi (Huxley, 1859) (type) L. declivus (Owen, 1860) L. curvatus (Owen, 1876) L. maccaigi Seeley, 1898 L. georgi Kalandadze, 1975 Lystrosaurus amphibius Lystrosaurus bothai Lystrosaurus breyeri Lystrosaurus broomi Lystrosaurus hedini Lystrosaurus jeppei Lystrosaurus jorisseni Lystrosaurus latifrons Lystrosaurus primitivus Lystrosaurus putterilli Lystrosaurus rajurkari Lystrosaurus robustus Lystrosaurus rubidgei Lystrosaurus theileri Lystrosaurus wageri Lystrosaurus wagneri Lystrosaurus weidenreichi Lystrosaurus youngi

Lystrosaurus (/ˌlɪstroʊˈsɔːrəs/; "shovel lizard") is herbivorous genus of Late Permian and Early Triassic Period dicynodont therapsids, which lived around 250 million years ago in what is now Antarctica, India, and South Africa. Four to six species are currently recognized, although from the 1930s to 1970s the number of species was thought to be much higher. They ranged in size from a small dog to 2.5 meters long.

Being 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. Lystrosaurus was a heavily built, herbivorous animal, approximately the size of a pig. The structure of its shoulders and hip joints suggests that Lystrosaurus moved with a semi-sprawling gait. The forelimbs were even more robust than the hindlimbs, and the animal is thought to have been a powerful digger that nested in burrows.

Lystrosaurus was by far the most common terrestrial vertebrate of the Early Triassic, accounting for as many as 95% of the total individuals in some fossil beds. It has often been suggested that it had anatomical features that enabled it to adapt better than most animals to the atmospheric conditions that were created by the Permian–Triassic extinction event and which persisted through the Early Triassic—low concentrations of oxygen and high concentrations of carbon dioxide. However, recent research suggests that these features were no more pronounced in Lystrosaurus than in genera that perished in the extinction or in genera that survived but were much less abundant than Lystrosaurus.