The end-Permian mass extinction event 250 million years ago was probably the most severe crisis in Earth history. Estimates suggest that more than 95% of life on Earth perished during this event. Marine life was hit hard. Besides the extinction of the trilobites and the tabulate and rugose corals, many other marine groups suffered near extinction including brachiopods, gastropods, cephalopods and crinoids. On land, the glossopterids, the dominant plant group in Gondwana (the southern Hemisphere) perished, and major floral changes occurred on a global scale. More than 70% of land-living vertebrate species died out.
But one group of land-living vertebrates appear almost unaffected by the end-Permian crisis, namely the parareptiles, an extinct group of reptiles, consisting of small to large tetrapods.
In a new paper in Palaeontology (read the abstract here) a group of researchers headed by Marcello Ruta recently presented various statistical analyses on diversity patterns of the Parareptilia. Their conclusion is that extinction rates for the parareptiles during the end-Permian event were no higher than before or after. However, only one clade of parareptiles crossed the Permian-Triassic boundary, and this accounted for all the Triassic parareptiles. So basically, all the other clades of parareptiles actually did die out prior to or during the end-Permian event, but as a group the parareptiles were hardly affected. It is not clear why this particular clade within the parareptiles was not affected by the end-Permian event when so many other terrestrial vertebrates were.
The parareptiles finally did go extinct – In the Rhaetian…