Tritylodon

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Tritylodon
Temporal range: Early Jurassic
Tritylodon longaevus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Family: †Tritylodontidae
Genus: †Tritylodon
Owen, 1884
Type species
Tritylodon longaevus
Owen, 1884
Species
  • T. longaevus Owen, 1884
  • T. maximus

Tritylodon (from the Greek for "three-cusped tooth") is an extinct genus of

synapsids.[1]

Characteristics

If a living Tritylodon were to be seen today, it would look a lot like a large rodent. They were about 30 centimetres (12 in) long but there is no certainty about the exact weight. Their method of chewing food, a grinding motion with the bottom teeth sliding against the top teeth, resembled that of rodents as well. The bottom teeth were much like a set of cusps and the top teeth were a set of matching grooves that matched perfectly allowing this motion. There were large incisors at the very front of their mouth separated by a gap from the rest of the teeth. The incisors would stick out and remain slightly visible when the mouth was closed. The legs were directly beneath the body like mammals, unlike the earlier therapsids with sprawling limbs.[citation needed]

These animals were burrowers; the structure of the shoulder, front limbs, and large front incisors show this. They used their incisors to help dig and unearth buried plants. The way they ate and the shape of their teeth demonstrate that Tritylodons were probably primarily

monotremes.[3]

Habitat

The Tritylodons' habitat was limited to the forests of South Africa When the species originated, about 200 million years ago, the African area was drier and hotter. But for most of their existence the climate was tropical and wetter.

Fossils

The Tritylodon fossils in South Africa are found concentrated mainly in an area about 11,000 km2 (4,250 mi2). They have been found in floodplain deposits of the Lower Jurassic Elliot Formation (upper Karoo Supergroup).[4] In this area there have been so many findings it has been named the Tritylodon Acme Zone.[5] The fossil findings have all been in the Free State of South Africa.[5]

The genus Tritylodon of the Tritylodonts is restricted to the South African forms: Tritylodon longaevus and Tritylodon maximus.[1] It is suggested that T. maximus is either a large T. longeavus or a closely related species. If it is a closely related species it could possibly be ecological succession since the larger T. maximus fossils have been dated in the Sinemurian–Pliensbachian mainly less than 190 million years ago and the T. longaevus in the Hettangian–Sinemurian mainly more than 190 million years ago. With the fossil findings of each species overlapping in Sinemurian stage, the fossils show two differences, T. maximus being larger and having nine upper postcanines (neither species had canine teeth) instead of the seven teeth like T. longeavus. All other structures of the two Tritylodon species were the same.[6][self-published source?]

Below is a cladogram from Ruta, Botha-Brink, Mitchell and Benton (2013) showing one hypothesis of cynodont relationships:[7]

Cynodontia
→ †Cynognathia
→ Probainognathia 

References

  1. ^ a b "Cynodontia: Tritylodontidae". Palaeos. Archived from the original on December 21, 2010.
  2. doi:10.4202/app.2008.0053
    .
  3. PMID 12532019
    .
  4. ^ Bordy, Emese M. (2008). "Enigmatic trace fossils from the Aeolian Lower Jurassic Clarens Formation, Southern Africa" (PDF). Palaeontologia Electronica. 11 (3).
  5. ^
    doi:10.1016/S0031-0182(96)00143-5
    .
  6. ^ http://home.arcor.de/ktdykes/jtherap.htm#tritylodon Archived 2010-04-23 at the Wayback Machine[full citation needed]
  7. PMID 23986112
    .

External links

Wikimedia Commons has media related to Tritylodon.
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