Dwykaselachus (pronounced dwike-a-selak-us) is an extinct genus of 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.[1]
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 chimaeras.[2] This implies that the first major radiation of cartilaginous fish after the Devonian extinction was in fact holocephalians, rather than sharks as commonly believed.[3]
^B.W. Oelofsen (1986). "A fossil shark neurocranium from the Permo-Carboniferous (lowermost Ecca Formation) of South Africa". In T. Uyeno; R. Arai; T. Taniuchi; K. Matsuura (eds.). Indo-Pacific Fish Biology: Proceedings of the Second International Conference on Indo-Pacific Fishes. Ichthyological Society of Japan. pp. 107–124. ISBN 978-4930813121.
^Coates, Michael I.; Gess, Robert W.; Finarelli, John A.; Criswell, Katharine E.; Tietjen, Kristen (2017). "A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes". Nature. 541 (7636): 208–211. Bibcode:2017Natur.541..208C. doi:10.1038/nature20806. PMID 28052054. S2CID 4455946.
of the shared similarities between Dwykaselachus and chimaeroids, suggesting symmoriiforms, including Dwykaselachus, comprise a sister clade to iniopterygians...
late Devonian. Most of them died out at the start of the Permian, but Dwykaselachus is known from the Artinskian-Kungurian of South Africa. Teeth described...
million years ago. Analysis of the 280 million-year-old holocephalian Dwykaselachus demonstrates that early members of the group were more shark-like. Kriwet...
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