Cynognathus

Cynognathus
Temporal range: Middle Triassic, 247–237 Ma
Fossil skull of Cynognathus
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Clade: Cynognathia
Family: Cynognathidae
Seeley, 1895
Genus: Cynognathus
Seeley, 1895
Type species
Cynognathus crateronotus
Seeley, 1895

Cynognathus is an extinct genus of large-bodied cynodontian therapsids that lived in the Middle Triassic. It is known from a single species, Cynognathus crateronotus. Cynognathus was a predator closely related to mammals and had a southern hemispheric distribution. Fossils have so far been recovered from South Africa, Argentina, Antarctica, and Namibia.

Description

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 and up to 2 metres (6 ft 7 in) in total length. It had a particularly large head, up to 40 centimetres (1 ft) in length, with wide jaws and sharp teeth. Its hindlimbs were placed directly beneath the body, but the forelimbs sprawled outwards in a more reptilian fashion. This form of double (erect/sprawling) gait is also found in some primitive mammals alive today.

Possible autapomorphies of C. crateronotus include an extremely elongated postorbital bar and sectorial postcanine teeth with two serrated cusps distal to a recurved apex.

Discovery and naming

Skull

During 1888 and 1889, the British paleontologist Harry Govier Seeley visited southern Africa. In 1889, near Lady Frere, at a location where earlier Alfred Brown had discovered a tooth, Seeley excavated a skull and partial postcranial skeleton of a cynodontian. In 1894, Seeley named the genus Cynognathus with as type species Cynognathus crateronotus. Simultaneously, he named three other species in the genus: Cynognathus berryi, honouring James Berry who had assisted in the excavations, Cynognathus platyceps, the "flat jaw", and Cynognathus leptorhinus, the "slender nose". The generic name Cynognathus is derived from Greek kyon and gnathos, meaning "dog jaw". In 1895, Seeley published a more comprehensive description of these finds.

Fossil material probably belonging to the genus has been given several different names over the years. Generic synonyms include Cynidiognathus, Cynogomphius, Karoomys, Lycaenognathus, Lycochampsa and Lycognathus. Opinions vary as to whether all remains belong to the same species. The genus Karoomys is known only from a tiny juvenile. Species-level synonyms of Cynognathus crateronotus include Cynidiognathus broomi, Cynidiognathus longiceps, Cynidiognathus merenskyi, Cynognathus berryi, Cynognathus minor, Cynognathus platyceps, Cynogomphius berryi, Karoomys browni, Lycaenognathus platyceps, Lycochampsa ferox, Lycognathus ferox, and Nythosaurus browni.

Distribution

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

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

This genus forms a Cynognathus Assemblage Zone in the Beaufort Group of the Karoo Supergroup.

Classification

Seeley in 1894/1895 placed Cynognathus in a separate family Cynognathidae, within the Cynodontia. Cynognathus is presently the only recognized member of the family Cynognathidae. Later a clade Cynognathia was named after the genus, within the Eucynodontia.

Cynognathus crateronotus in a cladogram after Stefanello et al. (2023):

Paleobiology

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 possible lack of belly 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.

See also


This page was last updated at 2024-04-18 09:50 UTC. Update now. View original page.

All our content comes from Wikipedia and under the Creative Commons Attribution-ShareAlike License.


Top

If mathematical, chemical, physical and other formulas are not displayed correctly on this page, please useFirefox or Safari