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Theriognathus
''Theriognathus'' (from Greek therion: beast, mammal, Greek, gnathos, “jaw,” +us, pronounced THEH-ree-OG-nah-thuss) is an extinct genus of therocephalian therapsid belonging to the family Whaitsiidae, from South Africa, Tanzania, and Russia. ''Theriognathus'' has been dated as existing during the Late Permian. Although ''Theriognathus'' means mammal jaw, the lower jaw is actually made up of several bones as seen in modern reptiles, in contrast to mammals. ''Theriognathus'' displayed many different reptilian and mammalian characteristics. For example, ''Theriognathus'' had canine teeth like mammals, and a secondary palate, multiple bones in the mandible, and a typical reptilian jaw joint, all characteristics of reptiles.〔 It is speculated that ''Theriognathus'' was either carnivorous or omnivorous based on its teeth, and was suited to hunting small prey in undergrowth. This mammal-like reptile adopted a sleek profile of a mammalian predator, with a narrow snout and around 1 meter long. ''Theriognathus'' is represented by 56 specimens in the fossil record.〔Chinsamy-Turan, Anusuya. Forerunners of Mammals: Radiation, Histology, Biology. Bloomington: Indiana University Press, 2012. http://site.ebrary.com.offcampus.lib.washington.edu/lib/uwash/detail.action?docID=10519688〕
==Geography==
''Theriognathus'' is represented by abundant occurrences in the Karoo Basin of South Africa, sequestered records in the Upper Permian Ruhuhu Basin of Tanzania, Zambia, and Russia.〔Sidor, C. A., D. A. Vilhena, K. D. Angielczyk, A. K. Huttenlocker, S. J. Nesbitt, B. R. Peecook, J. Sébastien Steyer, R. M. H. Smith, and L. A. Tsuji. 2013. Provincialization of terrestrial faunas following the end-Permian mass extinction. Proceedings of the National Academy of Sciences 110:8129–8133. http://www.pnas.org.offcampus.lib.washington.edu/content/110/20/8129.full〕 Late Permian therapsids are best known from the Karoo Basin, which covers a massive area and provides Permian sediments that total 12 km in thickness. During the Late Permian, sediments were fed into the Karoo Basin from a ring of mountains that encircled Southern Gondwana (an ancient supercontinent, partly located on what is now South America and Antarctica) In the Karoo is the Beaufort Group, a subdivision of the basin. This division is further broken down into assemblage zones, intervals of geological strata that are defined based on the distributions of previously found tetrapod taxa.〔Smith, Roger M. H, and Jennifer Botha-Brink. "Anatomy of a Mass Extinction: Sedimentological and Taphonomic Evidence for Drought-Induced Die-Offs at the Permo-Triassic Boundary in the Main Karoo Basin, South Africa." Palaeogeography, Palaeoclimatology, Palaeoecology. 396.7 (2014): 99-118. Print.〕
''Theriognathus'' has been found in the Wuchiapingian, upper Tropidostoma, Cistecephalus, and lower Dicynodon assemblage zones in the Upper Permian, Karoo Basin, South Africa; Wuchiapingian, Cistecephalus assemblage zones in the Upper Permian, Ruhuhu Basin, Tanzania; Wuchiapingian Cistecephalus assemblage zones in the Upper Permian, Luangwa Basin, Zambia; the Wuchiapingian, Upper Permian, Kotelnich, Kirov region, Russia;, the Changxingian Archosaurus assemblage zone, Upper Permian, Vladimir region, Russia.〔Huttenlocker, Adam K, and Christian A. Sidor. The Paleobiology of South African Therocephalian Therapsids (amniota, Synapsida) and the Effects of the End-Permian Extinction on Size, Growth, and Bone Microstructure. , 2013. https://digital.lib.washington.edu/researchworks/handle/1773/24299〕
''Theriognathus'' was also found in the Tapinocephalus assemblage zone, which was an odd find since most specimen in that zone tend to be medium to large in size. Theriognathus was an exception to that norm. Diversification was shown by an increase in richness of eutherocephalian groups in the Cistecephalus and Dicynodon assemblage zones. During this time some of the more specialized genera, including ''Theriognathus'', split from pre-existing families.〔
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