Dicynodonts
| Dicynodonts Temporal range: Middle Permian to Late Triassic (Possible Early Cretaceous record.) |
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| Skull of the dicynodont Endothiodon angusticeps in the American Museum of Natural History | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | Therapsida |
| Suborder: | †Anomodontia |
| Clade: | †Chainosauria |
| Infraorder: |
†Dicynodontia Owen, 1859 |
| Clades & Genera | |
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see "Taxonomy" |
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see "Taxonomy"
Dicynodontia is a taxon of anomodont therapsids or synapsids with beginnings in the mid-Permian, which were dominant in the Late Permian and continued throughout the Triassic, with a few possibly surviving into the Early Cretaceous. Dicynodonts were herbivorous animals with two tusks, hence their name, which means 'two dog tooth'. They are also the most successful and diverse of the non-mammalian therapsids, with over 70 genera known, varying from rat- to ox-sized.
The dicynodont skull is highly specialised, light but strong, with the synapsid temporal openings at the rear of the skull greatly enlarged to accommodate larger jaw muscles. The front of the skull and the lower jaw are generally narrow and, in all but a number of primitive forms, toothless. Instead, the front of the mouth is equipped with a horny beak, as in turtles and ceratopsian dinosaurs. Food was processed by the retraction of the lower jaw when the mouth closed, producing a powerful shearing action, which would have enabled dicynodonts to cope with tough plant material. Many genera also have a pair of tusks, which it is thought may have been an example of sexual dimorphism.
The body is short, strong and barrel-shaped, with strong limbs. In large genera (such as Dinodontosaurus) the hindlimbs were held erect, but the forelimbs bent at the elbow. Both the pectoral girdle and the ilium are large and strong. The tail is short.
Dicynodonts have long been suspected of being warm-blooded animals. Their bones are highly vascularised, possess Haversian canals and their bodily proportions are conductive to heat preservation. In young specimens, the bones are so highly vascularised that they exhibit higher channel densities than most other therapsids. Yet, studies on Late Triassic dicynodont coprolites paradoxically showcase digestive patterns more typical of animals with slow metabolisms.
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