In Depth
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. Mart�nez & Oscar A. Alcober – 2013.
