Diadectes
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| Diadectes Fossil range: Early Permian |
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 restoration of Diadectes
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D. absitus Berman et al., 1998 |
Diadectes was a genus of large, very reptile-like tetrapods that lived during the Early Permian. It is one of the very first herbivorous tetrapods, and also one of the first fully terrestrial animals to attain large size.
Diadectes was a heavily built animal, 1.5 to 3 meters long, with a thick-boned skull, heavy vertebrae and ribs, massive limb girdles and short, robust limbs. The nature of the limbs and vertebrae clearly indicate a terrestrial animal.
It possesses some characteristics of reptilians and amphibians, combining a reptile-like skeleton with a more primitive, seymouriamorph-like skull. Diadectes has been classified as a stem-amniote close to the ancestry of amniotes.
Among its primitive features, Diadectes has a large otic notch (a feature found in Paleozoic amphibians) with an ossified tympanum.
At the same time its teeth show advanced specialisations for a herbivorous diet that are not found in any other type of early Permian animal. The eight front teeth are spatulate and peg-like, and served as incisors that were used to nip off mouthfuls of vegetation. The broad blunt cheek teeth show extensive wear associated with occlusion, and would have functioned as molars, grinding up the food.
It also had a partial secondary palate, which meant it could chew its food and breath at the same time, something many even more advanced reptiles were unable to do.
Diadectes fossil remains are known from a number of locations across North America, but especially the Texas Red Beds (Wichita and Clear Fork).
[edit] References
- Benton, M. J. (2000), Vertebrate Paleontology, 2nd ed. Blackwell Science Ltd
- Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.
- Colbert, E. H., (1969), Evolution of the Vertebrates, John Wiley & Sons Inc (2nd ed.)
- Reisz, Robert, (no date), Biology 356 - Major Features of Vertebrate Evolution - Anthracosaurs and Diadectomorphs
