Ichthyopterygian

Fossil remains of derived marine ichthyopterygians, and the oldest ichthyopterygian remains to date, are known from the Olenekian aged Vikinghøgda Formation of Spitsbergen (Svalbard). These rocks are dated to just 2 million years after the Permian-Triassic extinction event, indicating that ichthyopterygians at the very least originated very early in the Triassic, before the Late Smithian crisis (a widespread ocean anoxic event that may have allowed ichthyopterygians to dominate deeper waters and temnospondyls to dominate shallow waters) and that ichthyosauromorphs as a whole originated during the Permian and were survivors of the Permian-Triassic mass extinction.