viraptor

Oviraptor lived in the late Cretaceous period, during the late Campanian stage about 75 million years ago; only one definitive specimen is known (with associated eggs), from the Djadokhta Formation of Mongolia, though a possible second specimen (also with eggs) comes from the northeast region of Inner Mongolia, China, in an area called Bayan Mandahu.

Oviraptor philoceratops is known from a single partial skeleton (specimen number AMNH 6517), as well as a nest of about fifteen eggs that have been referred to this species (AMNH 6508).

When living, Oviraptor was one of the most bird-like of the theropod dinosaurs. Its rib cage, in particular, displayed several features that are typical of birds, including a set of processes on each rib that would have kept the rib cage rigid. A relative of Oviraptor called Nomingia was found with a pygostyle, which is a set of fused vertebrae that would later help support the tail feathers of birds. Skin impressions from more primitive oviraptorosaurs, like Caudipteryx and Protarchaeopteryx, clearly show an extensive covering of feathers on the body, feathered wings and feathered tail fans. A tail fan is also indicated by the presence of a pygostyle in Nomingia, suggesting that this feature was widespread among oviraptorosaurs. Additionally, the nesting position of the brooding Citipati specimens implies the use of feathered wings to cover the eggs. Given the close anatomical similarity between these species and Oviraptor, it is highly likely that Oviraptor had feathers as well.

Oviraptor is traditionally depicted with a distinctive crest, similar to that of the cassowary. However, re-examination of several oviraptorids show that this well-known, tall-crested species may actually belong to the genus Citipati, a relative of Oviraptor. It is likely that Oviraptor did have a crest, but its exact size and shape are unknown due to crushing in the skull of the only recognized specimen.

The Oviraptor has two long, well developed hind limbs, each had three clawed fingers that were used to hold, rip and tear their prey. The Oviraptor had large eyes with bony rings and a unusual cranial crests along with a toothless beak.

As its name suggests, Oviraptor was originally presumed to have eaten eggs, based on its association with a fossilized nest (specimen number AMNH FR 6508) thought to belong to Protoceratops. The idea of a crushing jaw was first proposed by H. F. Osborn, who believed that the toothless beak of the original skull, together with an extension of several bones below the jaw from the palate, would have made an "egg-piercing" tool. In 1977, Barsbold argued that the strength of its beak would indicate that it was strong enough to break the shells of mollusks such as clams, which are found in the same geological formation as Oviraptor. These bones form part of the main upper jaw bone or maxilla, which converge in the middle to form a pair of prongs. The rest of the bony palate, unlike all other dinosaurs, is extended below the jaw line and would have pushed into the space between the toothless lower jaws. A beak (rhamphotheca) covered the edges of the upper and lower jaws and probably the palate, as proposed by Barsbold and Osborn.

The discovery of nesting specimens of the related Citipati, with the same types of egg in the original Oviraptor specimen, showed that the eggs actually belonged to Oviraptor, not Protoceratops, and that the type specimen was likely brooding the eggs, not feeding on them. While this discovery did not rule out the possibility that Oviraptor included eggs in its diet, its exact feeding strategies remain unknown. The only Oviraptor philoceratops skeleton preserved the remains of a lizard in the region of its stomach cavity, implying that the species was at least partially carnivorous.





from Wikipedia