Eoraptor

Eoraptor is one of the earliest known theropod dinosaurs. It was a very small omnivore or carnivore which lived in the Lower Triassic, about 245 million years ago (mya). It is the only one of the possible early dinosaurs which can be exactly dated by a layer of volcanic ash close beneath the fossil.

Eoraptor
Reconstructed skeleton, Royal Ontario Museum
Scientific classification
Unrecognized taxon (fix):	Eoraptor
Species:	Template:Taxonomy/EoraptorE. lunensis
Binomial name
Eoraptor lunensis Sereno et al., 1993

Eoraptor was a small, lightly-built archosaur that walked on two long legs. It was about 1 m (3.3 ft) it had light, hollow bones, a long head with dozens of small, sharp teeth, and five fingers on its grasping hands (two of the fingers on each hand were very small).

The fossil was found in the Ischigualasto Formation in the Argentine. This contains some of the oldest known dinosaur and archosaur remains. They are of top quality, number and importance. It is the only place in the world where nearly all of the Triassic is represented in an undisturbed sequence of strata. What is now badlands was then a volcanically active floodplain dominated by rivers, with a strongly seasonal rainfall.

Rhynchosaurs and cynodonts are by far the most common among the tetrapod fossils in the park. Dinosaurs make up only 6% of the findings, but these include early samples of the two major lineages of dinosaurs (ornithischians and saurischians). The carnivorous Herrerasaurus is the most numerous of these dinosaur fossils.

Teeth

The teeth of Eoraptor are of two types. There are serrated, recurved teeth in the maxillae (upper jaws), like the teeth of theropods, and leaf-shaped teeth in the dentary (lower jaw), like the teeth of basal sauropodomorphs.

Cladogram

Below is a cladogram based on the phylogenetic analysis conducted by Sues et al. in 2011, showing the relationships of Eoraptor:

Theropoda	Herrerasauridae  Staurikosaurus Herrerasaurus Chindesaurus Eoraptor Daemonosaurus Tawa  Neotheropoda   Coelophysidae  Megapnosaurus Coelophysis Liliensternus Zupaysaurus Cryolophosaurus Dilophosaurus Jurassic theropods

Replica skeleton in Japan

A large analysis of early dinosaurs by Matthew Baron, David Norman and Paul Barrett (2017) found Eoraptor to be the earliest diverging member of Theropoda, within the larger clade Ornithoscelida.

Eoraptor Media

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  産状骨格なのに浮いてる。

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  Eoraptor skull cast

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  Eoraptor compared in size to a human

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  Skeleton of Eoraptor lunensis, known remains depicted in white and light grey, unknown in dark grey.

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  Life reconstruction of Eoraptor lunensis

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  Herrerasaurus (large), Eoraptor (small), and Plateosaurus (skull), three early saurischians

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  Staurikosaurus pricei white background

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  Royal Ontario Museum Eoraptor white background

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  Eodromaeus murphi

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  Coelophysis (1) white background