What is Lystrosaurus?
{{italictitle}} {{automatic taxobox | fossil_range = Upper [[Permian]]–[[Lower Triassic]], 255{{ndash}}250 mya | image = Lystrosaurus hedini IMG 4469.jpg | image_upright = 1.15 | image_caption = ''Lystrosaurus hedini'' skeleton exposed at the Natural history museum of [[Zürich]] | taxon = Lystrosaurus | authority = [[Edward Drinker Cope|Cope]], [[1870 in paleontology|1870]] | subdivision_ranks = Species | subdivision = {{collapsible list|bullets = true|title=<small>List</small> | ''L. murrayi'' <small>([[Thomas Henry Huxley|Huxley]], 1859) ([[Type species|type]])</small> | ''L. declivis'' <small>([[Richard Owen|Owen]], 1860)</small> | ''L. curvatus'' <small>(Owen, 1876)</small> | ''L. maccaigi'' <small>[[Harry Seeley|Seeley]], 1898</small> }}}} '''''Lystrosaurus''''' is an extinct [[genus]] of [[herbivore|herbivorous]] [[dicynodont]] [[therapsid]] from the late [[Permian]] and [[Lower Triassic]] [[epoch (geology)|epochs]] (about 250 million years ago). It lived in what is now [[Antarctica]], [[India]], [[China]], [[Mongolia]], [[Russia]] and [[South Africa]]. Four to six species are known. They ranged in size from that of a small dog to 2.5 meters long.<ref>{{cite book |last1=Cluver |first1=Michael Albert |title=Fossil reptiles of the South African Karoo |date=1978 |publisher=The South African Museum |isbn=9780908407583 |language=en }}</ref> ''Lystrosaurus'' survived the [[Permian-Triassic extinction event]], 252 million years ago. In the [[Lower Triassic]], they were the most common terrestrial vertebrates. In some fossil beds they make up as many as 95% of the individuals.<ref name=Barendskraal>{{cite journal |author1=Damiani R.J. |author2=Neveling J. |author3=Modesto S.P. |author4=Yates A.M. |name-list-style=amp |year=2004 |title=Barendskraal, a diverse amniote locality from the ''Lystrosaurus'' assemblage zone, Early Triassic of South Africa |journal=Palaeontologia Africana |volume=39 |pages=53–62 }}</ref> Researchers have offered various ideas for why they survived the extinction and thrived in the ear