Eoraptor

Name: Eoraptor ‭(‬Dawn thief‭)‬.
Phonetic: E-owe-rap-tore.
Named By: Sereno,‭ ‬Forster,‭ ‬Rogers‭ & ‬Monetta‭ ‬-‭ ‬1993.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Saurischia,‭ ‬Eusaurischia.
Species: E.‭ ‬lunensis‭ (‬type‭)‬.
Diet: Possibly an omnivore.
Size: 1‭ ‬meter long.
Known locations: Argentina‭ ‬-‭ ‬Ischigualasto Formation.
Time period: Ladinian of the Triassic.
Fossil representation: Many specimens,‭ ‬some of which are very well preserved.

       Eoraptor stands out not only for being one of the first dinosaurs to ever walk the Earth,‭ ‬but because palaeontologists cannot conclusively agree on where to place it in relation to other dinosaurs.‭ ‬Initially Eoraptor was classed as a theropod because of its bipedal stance and narrow build,‭ ‬but the sauropodomorphs‭ (‬which would go on to evolve into giant quadrupedal dinosaurs like Apatosaurus and Brachiosaurus‭) ‬were also bipedal with a similar body plan in their early stages of development.‭ ‬To confuse things further,‭ ‬Eoraptor had two main types of teeth,‭ ‬those of a carnivore and a herbivore.‭ ‬This is why Eoraptor has in the past been classed as a theropod by some and sauropodomorph by others,‭ ‬and why in‭ ‬2011‭ ‬it was classed again as a eusaurischid,‭ ‬a position that places it between these two groups.
       The combination of the two types of teeth has been seen to suggest that Eoraptor was a generalist omnivore that adapted to the availability of different food and prey.‭ ‬Still,‭ ‬Eoraptor may have had a preference for one type of diet but still feeding upon another type to balance out nutritional deficiencies that were in the other.‭ ‬Eoraptor also lacked specialist carnivore adaptations such as a sliding jaw joint,‭ ‬which meant that Eoraptor would have been limited to small prey animals such as insects and lizards.
       Despite potentially carnivorous aspects of its diet,‭ ‬Eoraptor was not the dominant hunter of its day,‭ ‬and may itself have been prey to the larger Herrerasaurus that is also known from the same time and formation.

Further reading
- Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria. Nature 361:64-66 - P. C. Sereno, C. A. Forster, R. R. Rogers & A. M. Monetta - 1993.
- Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha). Basal sauropodomorphs and the vertebrate fossil record of the Ischigualasto Formation (Late Triassic: Carnian-Norian) of Argentina. - Journal of Vertebrate Paleontology Memoir 12: 83-179 - Paul C. Sereno, Ricardo N. Martínez & Oscar A. Alcober - 2013.



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