Trirachodon
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Trirachodon Temporal range: Early Triassic - Middle Triassic |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | Therapsida |
| Suborder: | Cynodontia |
| Family: | †Trirachodontidae |
| Subfamily: | †Trirachodontinae |
| Genus: |
†Trirachodon Seeley, 1895 |
| Species | |
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Trirachodon (Greek: "three ridge tooth") is an extinct genus of tritylodontoid cynodont. Fossils have been found from the Cynognathus Assemblage Zone of the Beaufort Group in South Africa, dating back to the Early and Middle Triassic.
The skull of Trirachodon had a short, narrow snout with a wide orbital region. The zygomatic arches were relatively slender.Trirachodon was quite small for a cynodont, growing no larger than 50 cm in length. It had noticeably less molariform teeth than its closely related contemporary Diademodon. These teeth tended to be transversely broader than Diademodon as well. A bony secondary palate and precise postcanine tooth occlusion are seen as derived characteristics in Trirachodon that are similar to those of mammals.
The type species is T. berryi, named in 1895 on the basis of a single cranial skeleton. Three other specimens were later referred to T. kannemeyeri, which was distinguished from the type on the basis of snout length and number of postcanine teeth. These differences have since been considered to small to assign them to two different species, and thus the T. kannemeyeri has fallen out of use due to this possible synonymy.
A new species, T. minor, was named by Robert Broom in 1905 to describe a poorly preserved snout. Broom later named T. browni in 1915, in which he distinguished it from all other species on the basis of the length of the molars. In 1932, Broom proposed that T. berryi be reassigned to a new genus, Trirachodontoides. Another species of Trirachodon called T. angustifrons was named in 1946 from a narrow skull found in Tanzania, but this material was later proven to be from the traversodontid Scalenodon. All species of Trirachodon were suggested to by synonymous with the type species in 1972 except T. browni, which was reassigned to Diademodon tetragonus.
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