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Symmoriiformes
Symmoriiformes is an extinct order of cartilaginous fish. Originally named Symmoriida by Zangerl (1981), the name has since been corrected to Symmoriiformes to avoid confusion with a family. The symmoriiform fossils record begins during the late Devonian, and most had become extinct by the start of the Permian, with the genus '' Dwykaselachus'' from the Artinskian-Kungurian of South Africa being the latest known uncontroversial occurrence. Teeth described from the Valanginian of France and Austria indicate that members of the family Falcatidae might have survived until the Early Cretaceous; however, it has since been proposed that these teeth more likely belonged to neoselachian sharks. Fossil distribution Fossil evidence of Symmoriida have been found at Bear Gulch, Fergus County, Montana, Bethel Quarry, Pike County, Indiana, Kinshozan quarry, Alaska, Gifu Prefecture, Japan, Bashkortostan, Russian Federation and possibly also France. Classification Symmoriiformes were previ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dwykaselachus
''Dwykaselachus'' (pronounced dwike-a-selak-us) is an extinct genus of Symmoriiformes, symmoriiform, a cartilaginous fish that lived in what is now South Africa during the Permian period around 280 million years ago. It was first discovered in the 1980s, in a nodule of sediments from the Karoo Supergroup. ''Dwykaselachus'' was named based on Dwyka Group, the group of sedimentary geological formation in the southeastern part of Africa. It represents the place where the type species ''Dwykaselachus oosthuizeni'' was found. Prior to its discovery, symmoriiforms were thought to be related to sharks, in the group Elasmobranchii. However, CT scans of its relatively intact skull showed traits such as brain shape and inner ear structure that are shared with cartilaginous fish from the group Holocephali, which includes Chimaera, chimaeras. This implies that the first major radiation of cartilaginous fish after the Late Devonian extinction, Devonian extinction was in fact holocephalians, r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |