Cynognathus

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Cynognathus
Temporal range: Middle Triassic, 247–237 Ma
Cynognathus crateronotus - National Museum of Natural History - IMG 1987.JPG
Fossil skull of Cynognathus crateronotus
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Order: Therapsida
Suborder: Cynodontia
Family: Cynognathidae
Seeley, 1895
Genus: Cynognathus
Seeley, 1895
Type species
Cynognathus crateronotus
Seeley, 1895

Cynognathus is an extinct genus of large-bodied cynodont therapsids that lived in the Middle Triassic. It is known from a single species, Cynognathus crateronotus. Cynognathus was a 1.2-metre (3 ft 11 in) long[1] predator closely related to mammals and had a southern hemispheric distribution. Fossils have so far been recovered from South Africa, Argentina, Antarctica, and Namibia.

Taxonomy[edit]

Skull

The genus Cynognathus (from Greek κυνόγναθος, meaning "dog jaw") has been given several different names over the years. It has also been known as Cistecynodon, Cynidiognathus, Cynogomphius, Karoomys, Lycaenognathus, Lycochampsa and Lycognathus. Cynognathus is the only recognized member of family Cynognathidae. Opinions vary as to whether all remains belong to the same species.

Species-level synonyms of Cynognathus crateronotus include Cistecynodon parvus, Cynidiognathus broomi, Cynidiognathus longiceps, Cynidiognathus merenskyi, Cynognathus beeryi, Cynognathus minor, Cynognathus platyceps, Cynogomphius berryi, Karoomys browni, Lycaenognathus platyceps, Lycochampsa ferox, Lycognathus ferox, and Nythosaurus browni.

The genera Karoomys and Cistecynodon are known only from tiny juveniles.

Description[edit]

Life reconstruction of Cynognathus crateronotus

Cynognathus was a heavily built animal, and measured around 1.2 metres (3 ft 11 in) in snout-to-vent body length. It had a particularly large head, 30 centimetres (1 ft) in length, with wide jaws and sharp teeth. Its hind limbs were placed directly beneath the body, but the fore-limbs sprawled outwards in a reptilian fashion.[2] This form of double (erect/sprawling) gait is also found in some primitive mammals alive today.[3]

The dentary was equipped with differentiated teeth that show this animal could effectively process its food before swallowing. The presence of a secondary palate in the mouth indicates that Cynognathus would have been able to breathe and swallow simultaneously.

The lack of ribs in the stomach region suggests the presence of an efficient diaphragm: an important muscle for mammalian breathing. Pits and canals on the bone of the snout indicate concentrations of nerves and blood vessels. In mammals, such structures allow hairs (whiskers) to be used as sensory organs.

Provenance[edit]

Distribution of four Permian and Triassic fossil groups used as biogeographic evidence for continental drift, and land bridging. Location of Cynognathus remains shown by red diamonds

Fossils have been found in Karoo, the Puesto Viejo Formation, Fremouw Formation, in South Africa/Lesotho, Argentina and Antarctica.

Cynognathus lived between the Anisian and the Ladinian (Middle Triassic).[4]

This genus forms a Cynognathus Assemblage Zone in the Beaufort Group of the Karoo Supergroup.[5][6][7]

See also[edit]

References[edit]

  1. ^ Jones & Bartlett Learning, Strickberger's Evolution, 2008
  2. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 193. ISBN 1-84028-152-9.
  3. ^ Jenkins, Farish A. (20 August 2009). "Limb posture and locomotion in the Virginia opossum (Didelphis marsupialis) and in other non-cursorial mammals". Journal of Zoology. 165 (3): 303–315. doi:10.1111/j.1469-7998.1971.tb02189.x. Retrieved 4 May 2012.
  4. ^ Trewick, Steve (2016). International Encyclopedia of Geography: People, the Earth, Environment and Technology. John Wiley & Sons, Ltd. doi:10.1002/9781118786352.wbieg0638. ISBN 9781118786352.
  5. ^ A threefold subdivision of the Cynognathus Assemblage Zone (Beaufort Group, South-Africa) and its paleogeographic implications. PJ Hancox, MA Shishkin, BS Rubidge, JW Kitching, South African Journal of Science, 1995
  6. ^ Vertebrate burrow complexes from the Early Triassic Cynognathus Zone (Driekoppen Formation, Beaufort Group) of the Karoo Basin, South AfricaGH Groenewald, J Welman, JA MacEachern - Palaios, 2001
  7. ^ Stratigraphic and sedimentological investigation of the contact between the Lystrosaurus and the Cynognathus assemblage zones (Beaufort group: Karoo supergroup). J Neveling - Bulletin of the Council for Geoscience, 2004

Further reading[edit]

  • Seeley (1895), "Researches on the structure, organization, and classification of the fossil Reptilia. Part IX., Section 5. On the skeleton in new Cynodontia from the Karroo rocks". Phil. Transactions of the Roy. Soc. of London, series B 186, p. 59–148.