Eoraptor
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Eoraptor Temporal range: Late Triassic, 231.4 Ma |
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| Restored skeleton, Royal Ontario Museum | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Order: | Saurischia |
| Clade: | Eusaurischia |
| Genus: |
†Eoraptor Sereno et al., 1993 |
| Species: | †E. lunensis |
| Binomial name | |
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Eoraptor lunensis Sereno et al., 1993 |
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Eoraptor (pron.: UK, Aus, NZ /ˈi.oɹɑptə/; US, Can /ˈi.oɹæptɚ/) was one of the world's earliest dinosaurs that lived ca. 231.4 million years ago, during the latter part of the Triassic Period in Western Gondwana, what is now the northwestern region of Argentina. It was a small sized, lightly-built, ground-dwelling, two-legged bipedal saurischian. It is known from several well-preserved skeletons. When first described in 1993, it was considered to be one of the earliest, if not the earliest known dinosaur. Eoraptor has heterodont dentition, suggesting that it was omnivorous, and that this feeding strategy had evolved early on in dinosaurs.
Eoraptor had a slender body that grew to about 1 meter (3.3 ft) in length, with an estimated weight of about 10 kilograms (22 lb). It had a lightly built skull with a slightly enlarged external naris. Like the coelophysoids which would appear millions of years later, Eoraptor had a kink in its upper jaws, between the maxilla and the premaxilla. Sereno et al. (2013) observed that the lower jaw had a mid-mandibular joint. It ran digitigrade, and upright on its hind legs. The femur of the holotype specimen PVSJ 512 of Eoraptor is 152 mm, and the tibia is 157 mm, suggesting that it was a fast runner. Its forelimbs are only half the length of its hindlimbs, which would suggest that it was an obligate biped. All of its long bones have hollow shafts.Eoraptor had five digits on each 'hand', the three longest of which ended in large claws and were presumably used to handle prey. Scientists have surmised that the fourth and fifth digits were too tiny to be of any use in hunting. The ilium is supported by three sacral vertebrae, unlike that of the coeval Herrerasaurus which is supported by only two sacrals, a basal trait.Eoraptor had vertebral centra that are hollow, a feature present in some of its ancestors.
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