Ctenosauriscus

Ctenosauriscus (meaning "Ctenosaura-like") is an extinct genus of sail-backed poposauroid archosaur from Early Triassic deposits of Lower Saxony in northern Germany. It gives its name to the family Ctenosauriscidae, which includes other sail-backed poposauroids such as Arizonasaurus. Fossils have been found in latest Olenekian deposits around 247.5-247.2 million years old, making it one of the first known archosaurs.

==History of discovery== Ctenosauriscus is known from the holotype, GZG.V.4191, a single partial preserved postcranial skeleton including partial vertebral column, ribs and girdle. The holotype is composed of four slabs, which were labeled A1, A2, B1, and B2 in a 2011 study. Slabs A1 and B1 form the part and slabs A2 and B2 form the counterpart. The holotype was discovered in early 1871 in the Bremke dell locality, near the county of Göttingen. The holotype was found in a deposit called the Solling-Bausandstein, which is an outcropping of the upper Middle Buntsandstein in the region of Eichsfeld. After the holotype was uncovered, it was housed in the University of Göttingen . It remained undescribed until 1902, when German paleontologist Friedrich von Huene designated it to the new species Ctenosaurus koeneni. thumb|left|Edaphosaurus and Platyhystrix, two sail-backed animals from the Early Permian. Ctenosauriscus was first classified as a [[pelycosaur similar to Edaphosaurus, and later as a temnospondyl closely related to Platyhystrix.]] Von Huene considered C. koeneni to be a late-surviving species of Pelycosauria, a group of distant mammal relatives otherwise known only from the Late Carboniferous and Early Permian. He based this classification on its similarity with sail-backed pelycosaurs like Dimetrodon. Austrian paleontologist Othenio Abel placed C. koeneni as a temnospondyl amphibian closely related to the sail-backed Platyhystrix (which, like Dimetrodon, was from the Early Permian). The name Ctenosaurus was preoccupied by a species of iguanid lizard (now called Ctenosaura), so a new generic name, Ctenosauriscus, was erected by paleontologist Oskar Kuhn in 1964. Paleontologist B. Krebs redescribed the holotype and reclassified Ctenosauriscus as an archosaur based on similarities with the sail-backed pseudosuchian Hypselorhachis from the Middle Triassic Manda Beds of Tanzania. thumb|Fragmentary material which has been referred to this genus Ctenosauriscus was found in the Solling Formation, which was deposited about 247.5 to 247.2 million years ago in the latest Olenekian stage. This age is based on radiometric dating and records of Milankovitch cycles in the formation. Ctenosauriscus was traditionally thought to have lived during the Middle Triassic after Krebs placed the Middle Buntsandstein within the Anisian stage.