Cynognathus was a metre-long predator of the Lower Triassic. It was one of the more mammal-like of the ‘mammal-like reptiles’, a member of a grouping called Eucynodontia.

Cynognathus had a more or less worldwide distribution. Fossils have so far been recovered from South Africa, South America, China and Antarctica. This genus has been given a lot of different names over the years.

Genus: Cynognathus

Meaning of name: 'Dog jaw'. Also known as: Cistecynodon, Cynidiognathus, Cynogomphius, Karoomys, Lycaenognathus, Lycochampsa, Lycognathus, Nythosaurus. In addition, according to the records of the Peabody Museum, Yale University, Richard Owen used the name Nythosaurus for this animal in 1876. This usage seems to be unconnected with Cynognathus. Cynognathus is presently the only recognized member of a family called Cynognathidae. Opinions vary as to whether all remains belong to the same species.

Species: Cynognathus crateronotus

Also known as: Cistecynodon parvus, Cynidiognathus broomi, Cynidiognathus longiceps, Cynidiognathus merenskyi, Cynognathus beeryi, Cynognathus minor, Cynognathus platyceps, Cynogomphius berryi, Karoomys browni, Lycaenognathus platyceps, Lycochampsa ferox, Lycognathus ferox, Nythosaurus browni. 15 different names for one Mesozoic creature might be regarded as excessive, but it's by no means a record. The dinosaur Plateosaurus engelhardti, has been named well over 20 times.
Karoomys, Cistecynodon and Nythosaurus are known only from tiny juveniles, whilst Lycognathus cucullatus seems to be a misidentified snake from the Balearic Islands, although confirmation is elusive.

Location of fossils: Karoo; Puesto Viejo Formation; Fremouw Formation, in South Africa/Lesotho; Argentina; Antarctica; China.

Age: Spathian, Lower Triassic - Anisian, Middle Triassic

Remarks: 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 cells. In mammals, such structures allow hairs (whiskers) to be used as sensory organs. All of these features indicate that Cynognathus was an endothermic animal: a ‘warm blooded’ creature with a relatively high metabolic rate, which needed to be able to process food and oxygen quickly.

Reference

• Seeley (1895), Researches on the structure, organization and classification of the fossil Reptilia. Part IX, section 1. On the Therosuchia. Phil. Transactions of the Roy. Soc. of London, series B 185 (21), p.987-1018.