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Cynognathidae

Cynognathus
Cynognathus
drawing by Steve Kirk - Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals, ed.. Barry Cox

A large and powerful preditor, and dominant animal for many millions of years, Cynognathus was one of the largest cynodonts. The head was proportionally very large (upto 30 to 45 cm in length) and somewhat doglike in appearance, hence the name Cynognathus ("dog jaw"). The skull is rather narrow, with a short temporal region, which served for the attachment of very powerful muscles for closing the jaws. Practically the whole of the lower jaw on each side was made up of a single bone, the dentary, into which were set the teeth the cutting incisors, stabbing canines and shearing cheek teeth. Behind the small, peglike incisors was a gap, followed by the large canine. A great bony flange (the coronoid process) at the back of the dentary articulated with the skull, and enabled the jaws to be opened wide. This flange also provided a large area to which extra jaw muscles could attach, giving the jaws tremendous bite-power.

The body also was strongly built, with its hindlimbs placed directly beneath its body. The knee pointed forward and the elbow backward, giving an erect mammalian posture. Clearly this was an efficient preditor, perfectly adapted to its environment, which persisted with little or no change for some five or ten million years. review of the cynodonts gives only a single species, but it is possible that there were several very similiar species, possibly in different parts of Pangea, and perhaps suceeding each other as the link to palaeos com Triassic period progressed.

Although a very succesful animal, Cynognathus died out during the link to palaeos com middle Triassic period, to be replaced by the smaller carnivorous Chiniquodontids and the small to large herbivorous Traversodontids. It is likely that the very arid conditions of the Triassic worked against the mammal-like Cynognathus and in favour of the reptilian link to palaeos com archosaurs (the Thecodonts) which had become the unchallanged masters of the land by the middle Triassic.

FAMILY CYNOGNATHIDAE Watson 1917

Includes: Karromysidae Haughton 1924a.

Ecological niche/Guild: large terrestrial carnivore
Modern equivalents: wolverine

Horizon: link to palaeos com early Triassic period: Cynognathus Zone of South Africa and Lesotho; Puesto Viejo Formation of Argentina; China.
Age: link to palaeos com Spathian to link to palaeos com Anisian
Distribution: Only known so far from link to palaeos com Gondwana, although it is not unlikely that these animals had a worldwide ( link to palaeos com Pangea) distribution, perhaps limited by local geographic or environmental factors.
preferred food: other tetrapods
length: about one and a half meters long
weight: the size of a large wolf - adults 50 to 70 kg
Metabolism: partially or completely endothermic
Potential Predators: large Erythosuchid thecodonts
Ancestor: Galesauridae
Replaced: Galesauridae
Replaced by: Chiniquodontidae
Descendents: Chiniquodontidae and Diademodontidae
Taxonomic status - monogeneric Family

List of genera

Genus Cynognathus Seeley 1895b.

Synonyms: Karoomys Broom 1903b; Lycognathus Broom 1913b; Lycochampsa Broom 1915b; Cynidiognathus Haughton 1922; Lycaenognathus Broom 1925; Cynogomphius Broom 1932; Cistecynodon Brink and Kitching 1953.

Cynognathus crateronotus Seeley 1 895b

Synonyms: Cynognathus berryi Seeley 1895b; Cynognathus platyceps Seeley 1895b; Karoomys browni Broom 1903b; Nythosaurus browni Broom 1912a; Lycognathus ferox 75 Broom 1913b; Lycochampsa ferox Broom 1915b; Cynidiognathus longiceps Haughton 1922; Cynidiognahus broomi Ilaughton 1922; Lycaenognathus platyceps Broom 1925; Lycaenognathus kannemeyerz Broom 1931; Cynogomphius berryi Broom 1932; Cynidiognathus merenskyi Broili and Schröder 1935b; Cistecynodon parvus Brink and Kitching 1953; Cynognathus minor Bonaparte 1967a.
Horizon: and Age: Same as for family.

Remarks: Generic and specific distinctions within the Cynognathidae have been based on characters which vary with age (tooth number and morphology, skull proportions) and are influenced by postmortem deformation. Karoomys, Cistecynodon, and Nythosaurus browni are based on tiny juveniles of Cynognathus. In their review of the Cynodontia Hopson and Kitching recognize only a single species, pending a thorough revision of the family.



some printed references some Links and References Web links

printed referenceCarroll, R. L. Vertebrate paleontology and evolution. -W. H. Freeman and company, New York, 1988

printed referenceEdwin H. Colbert, Evolution of the Vertebrates, 2nd edition, 1969, John Wiley & Sons

printed referenceBarry Cox, R.J.G. Savage, Brian Gardiner; Dougal Dixon, 1988 Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals

printed referenceJames A. Hopson, "The Origin and Adaptive Radiation of Mammal-Like Reptiles and Non-Therian Mammals, Annals of the New York Academy of Sciences 167:199-216, 1969

printed referenceJames A. Hopson and Herbert R. Barghusen, "An Analysis of Therapsid Relationships", in The Ecology and Biology of Mammal-Like Reptiles ed. by Nocholas Hotton III, Paul D. MacLean, Jan J. Roth and E. Carol Roth, Smithsonian Institute Press, Washington and London, 1986, pp.83-106

printed referenceJames A. Hopson and James W. Kitching, 1972, "A Revised Classification of the Cynodonts (Reptilia; Therapsida), Paleontologica Africa, 14. 17-85

Cynodont - a nice colour drawing of Cynognathus here



link to palaeos com Triassic Period Therapsida Theriodontia


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page by M.Alan Kazlev
page uploaded 6 September 2000. Reposted and last modified 1 September 2005, links updated 16 January 2010