Cynognathus
Name:
Cynognathus
dog jaw).
Phonetic: Sy-noe-nay-fuss.
Named By: Harry Govier Seeley - 1895.
Synonyms: Synonyms may include Cistecynodon
parvus, Cynidiognathus broomi, Cynidiognathus longiceps,
Cynidiognathus merenskyi, Cynognathus beeryi, Cynognathus minor,
Cynognathus platyceps, Cynogomphius berryi, Karoomys browni,
Lycaenognathus platyceps, Lycochampsa ferox and Lycognathus ferox,
though not all authors agree to the exact synonymy of these.
Classification: Chordata, Synapsida,
Therapsida, Cynodontia.
Species: C. crateronotus
(type), C. seeleyi.
Diet: Carnivore.
Size: Body length up to 1 meter long, Skull up
to 30 centimetres long.
Known locations: Antarctica, Argentina, China,
South Africa.
Time period: Anisian of the Triassic.
Fossil representation: Multiple fossils,
Cynognathus is one of the most numerous and completely reconstructed
cynodonts.
Cynognathus
seems to be one of the most successful of the cynodonts, with a large
number of fossil remains from a wide geographic distribution being all
attributed to the genus. There is however some controversy over
whether all of these fossils should be labelled as Cynognathus,
as
the genus does seem to have suffered from the ‘wastebasket taxon’
effect.
Despite
this the appearance of Cynognathus is known
without doubt. In
general appearance Cynognathus was a stocky animal
with a
proportionately large skull that made up thirty per-cent of the total
body length. The skull was robust and was likely capable of
inflicting powerful bites. The teeth were sharp, and slightly
re-curved, and driven by the jaw muscles were easily capable of
piercing the tough hides of the known herbivores of the early
Triassic. In addition they was some variance in the form of the teeth
suggesting that Cynognathus processed food by jaw
movement, cutting
meat up into smaller bits rather than just trying to swallow chunks
whole. The skull also features a hard secondary palate, something
that proves that Cynognathus would have still been
able to breathe when
the mouth was full of food.
The post cranial skeleton of Cynognathus is also quite interesting. The ribs do not extend into the abdomen which means two things. One is that Cynognathus likely had a diaphragm, a sheet of muscle that separates the lungs from the lower organs, a feature commonly seen in mammals that aids in respiration. Two is that the lower body would have been much more flexible thanks to the absence of the ribs. The rear legs of Cynognathus supported the hind quarters from underneath, but at the same time the front legs sprawled out to the sides like in more primitive therapsids. Although Cynognathus might have been an unusual runner, it was almost certainly fast enough to catch other therapsids.
Further reading
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. - Philosophical Transactions of
the Royal Society of London B 186:59-148 - Harry Govier Seeley
- 1895.
- The first occurrence of Cynognathus crateronotus
(Cynodontia:
Cynognathia) in Tanzania and Zambia, with implications for the age and
biostratigraphic correlation of Triassic strata in southern Pangea. -
B. M. Wynd, B. R. Peecock, M. R. Whitney & C. A. Sidor, In
Vertebrate and Climatic Evolution in the Triassic Rift Basins of
Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17.
Journal of Vertebrate Paleontology 37(6, Supplement) pp. 228–239, C.A.
Sidor & S.J. Nesbitt (eds.) - 2018.
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