Eoraptor (Dawn thief)
Eoraptor (Dawn thief)
Named By : Sereno, Forster, Rogers & Monetta - 1993
Diet : Possibly an Omnivore
Size : Estimated 1 meters long
Type of Dinosaur : Small Theropod
Type Species : E. lunensis (type)
Found in : Argentina - Ischigualasto Formation
When it Lived : Late Triassic, 228 million years ago
Eoraptor is a genus consisting of small, light-built, basal sauropodomorphs. It is one of the oldest-known dinosaurs. It lived between 231 and 228 million years ago in Western Gondwana in the area that is now northwestern Argentina. Eoraptor, the only known type of Eoraptor, was first described in 1993. It is known from a well-preserved and complete skeleton, as well as several fragmentary pieces. Eoraptor was multi-toothed, which indicates that it was an omnivore.
Ricardo Martinez, University of San Juan paleontologist, discovered the bones of this primitive dinosaur in 1991 during fieldwork at the University of Chicago, and the University of San Juan. The holotype PVSJ512 was found in the muddy siltstone of the Cancha de Bochas Member, Ischigualasto Formation in Argentina. These fossils were found in the Carnian stage, which was approximately 235- 228 million years ago. The collection of the holotype took nearly 12 months. It was then sent to Chicago’s Field Museum of Natural History for preparation by William F. Simpson, and Bob Masek. It was initially displayed in Chicago, but was returned to San Juan, Argentina where it was placed at the Museum of Natural Sciences.
Raymond R. Rogers and Alfredo M. Monetta, who described and named the genus Eoraptor in 1993, were Paul Sereno and Catherine Forster. Named after the Greek word Eos (eos), which means “dawn”, a reference its primitive nature, and the Latin term raptor, which means “plunderer”, a reference its presumed carnivorous nature as well as its grasping hand, the name derives from the Latin word Raptor. The Latin words luna (‘moon) and the suffix –ensis (‘inhabitant’), are the basis of the specific name lunensis. This is a reference the place where it was discovered: the Valle de la Luna, a deserted area that evokes a lunar landscape. Eoraptor, a type species, means “dawn plunderer of the Valley of the Moon”.
Eoraptor was a slim, slender creature with a length of approximately 1 m (3 ft 3in) and a weight of around 10 kg (22 lb). The skull was slender and had an externally slightly larger naris. Eoraptor, like early sauropodomorphs like Buriolestes and Pampadromaeus, had a kink between its maxillae and premaxilla. Paul Sereno et al. (2013) found that the lower jaw has a mid-mandibular joints. It ran digitigrade and stood upright on its hind legs. The holotype specimen PVSJ512’s femur measures 152 millimetres (6.0 inches), while the tibia measures 157 millimetres (6.8 in), which suggests that it was a quick runner. Its forelimbs measure only half of its hindlimbs. This suggests that it was bipedal. It has hollow shafts in all of its long bones. Eoraptor had five fingers on each hand. The three longest digits ended in large claws, and were likely used to catch prey. Scientists believe that the fourth and fifth fingers were too small to be useful in hunting. Three sacral vertebrae support the ilium (unusual of the two basal sauropodomorphic sacrals), which is a difference from the Herrerasaurus coeval, which has only two sacrals. Eoraptor’s vertebral centers were hollow, which is a characteristic that was present in its ancestors.
Bonaparte (1996) considered the large orbital opening of the skull to be a juvenile trait. Ronald Tykoski agreed with Bonaparte (2005). He suggested that the type specimen’s skull features suggested that it was young. These included a lack of complete fusion, large orbits and snout. Paul Sereno et al. (1993) Supported the idea that Eoraptor was an adult species based on the closures in the vertebral column and partial fusions of the scapulocoracoid.
Sereno and colleagues. According to Sereno et al. (1993), Eoraptor is distinguished by the fact that the anterior maxillary and premaxillary teeth of Eoraptor are leaf-shaped, with slightly larger external nares and a narrow posterolateral process. Max Langer (2006) and Michael Benton (2006) pointed out that Eoraptor is easily distinguished by the fact that its proximal fibula has a very transversely compressed proximal portion.