Oviraptor

Oviraptor Fossil range: Late Cretaceous
Bust of Oviraptor philoceratops
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Superorder: Dinosauria Order: Saurischia Suborder: Theropoda Family: Oviraptoridae Genus: Oviraptor Osborn, 1924
Species
O. philoceratops Osborn, 1924 (type)

Oviraptor is a genus of small Mongolian theropod dinosaur, first discovered by the legendary paleontologist Roy Chapman Andrews, and first described by Henry Fairfield Osborn, in 1924. Its name is Latin for 'egg seizer', referring to the fact that the first fossil specimen was discovered atop a pile of what were thought to be Protoceratops eggs, and the specific name philoceratops means "lover of ceratopsians", also given as a result of this find. In his 1924 paper, Osborn explained that the name was given due to the close proximity of the skull of Oviraptor to the nest (it was separated from the eggs by only four inches of sand). However, Osborn also suggested that the name Oviraptor "may entirely mislead us as to its feeding habits and belie its character."[1] In the 1990s, the discovery of nesting oviraptorids like Citipati proved that Osborn was correct in his caution regarding the name. These finds showed that the eggs in question probably belonged to Oviraptor itself, and that the specimen was actually brooding its eggs.

Oviraptor lived in the late Cretaceous Period, during the Santonian stage, and may have lived in an earlier stage called the Campanian, between 80 to 70 million years ago; it comes almost exclusively from the Djadokhta Formation of Mongolia, as well as the northeast region of the Neimongol Autonomous Region of China, in an area called Bayan Mandahu.

Description

Oviraptor philoceratops is known from a single partial skeleton (specimen number AMNH 6517), as well as a nest of about 15 eggs that have been referred to this species (AMNH 6508).

Oviraptor was one of the most bird-like of the non-avian 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.[2] 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.[3] 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.

Classification

Oviraptor was originally allied with the ornithomimids by Osborn due to its toothless beak. Osborn also found similarities with Chirostenotes, which is still considered a close relative of Oviraptor.[1] In 1976, Barsbold erected a new family to contain Oviraptor and its close kin, making Oviraptor the type genus of the Oviraptoridae.[4]

While the original specimens of Oviraptor were poorly preserved, especially the crushed and deformed skull, new and more complete oviraptorid specimens were assigned to the genus in the 1970s and 1980s. In 1976, Barsbold referred six additional specimens to the genus Oviraptor (including IGM 100/20 and 100/21)[4], but these were later reclassified in the new genus Conchoraptor.[5] Another specimen, IGN 100/42, is perhaps the most famous, owing to its well-preserved complete skull and large size. This specimen was referred to the genus Oviraptor by Barsbold in 1981[6] and came to represent Oviraptor in most popular depictions and in scientific studies of oviraptorids.[7] However, this specimen, with its distinctive tall, cassowary-like crest, was re-examined by the scientists who described the nesting oviraptorids, and found to resemble them more closely than the original specimens of Oviraptor. For this reason, they removed IGN 100/42 from the genus Oviraptor, provisionally re-classifying it as a species of Citipati.[3]

Paleobiology
As its name suggests, Oviraptor was originally presumed to have eaten eggs, based on its association with a fossilized nest.[1] However, 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. 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. 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 upper and lower jaws and probably the palate, as proposed by Barsbold and Osborn.

In popular culture

Thanks in part to its bizarre, bird-like appearance, and reputation as an egg thief, Oviraptor is a staple of popular fiction featuring dinosaurs. However, almost all popular depictions of Oviraptor have actually been based on earlier reconstructions of the tall-crested oviraptorid now known as Citipati, not on currently recognized specimens of Oviraptor.

One notable example of Oviraptor in fiction is its appearance in James Gurney's book Dinotopia. Because he no longer considered it a predator of eggs, Gurney renamed the animal "Ovinutrix", which means "egg nurse". Oviraptor is often depicted in dinosaur films, such as Disney's Dinosaur, in which one was shown stealing an Iguanodon egg, and in the first episode of the Discovery Channel television series Dinosaur Planet, competing for food with Velociraptor. Oviraptor has also appeared in several video games, including Dino Stalker and Dino Crisis 2, both of which erroneously depicted the animal as capable of spitting poison in the manner of the fictionalized Dilophosaurus from the film Jurassic Park. Ruby is a young female Oviraptor that befriends the young dinosaurs in The Land Before Time TV series.

References

1. ^ a b c Osborn, H.F. (1924). "Three new Theropoda, Protoceratops zone, central Mongolia." American Museum Novitates, 144: 12 pp., 8 figs.; (American Museum of Natural History) New York. (11.7.1924).
2. ^ Paul, G.S. (2002). Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Baltimore: Johns Hopkins University Press.
3. ^ a b Clark, J.M., Norell, M.A., & Barsbold, R. (2001). "Two new oviraptorids (Theropoda:Oviraptorosauria), upper Cretaceous Djadokhta Formation, Ukhaa Tolgod, Mongolia." Journal of Vertebrate Paleontology 21(2):209-213., June 2001.
4. ^ a b Barsbold, R. (1976). "A new Late Cretaceous family of small theropods (Oviraptoridae n. fam.) in Mongolia." Doklady Akademii Nauk SSSR, 226(3): 685-688.
5. ^ Barsbold, R. (1986). "Raubdinosaurier Oviraptoren" [in Russian]. In: O.I. Vorob’eva (ed.), Gerpetologičeskie issledovaniâ v Mongol’skoj Narod−noj Respublike, 210–223. Institut èvolûcionnoj morfologii i èkologii životnyh im. A.N. Severcova, Akademiâ nauk SSSR, Moscow.
6. ^ Barsbold, R. (1981). "Toothless dinosaurs of Mongolia." Joint Soviet-Mongolian Paleontological Expedition Transactions, 15: 28-39. [in Russian]
7. ^ Barsbold, R., Maryanska, T., and Osmolska, H. (1990). "Oviraptorosauria," in Weishampel, D.B., Dodson, P., and Osmolska, H. (eds.). The Dinosauria. Berkeley: University of California Press, pp. 249-258.

External links

* Oviraptor in The Dinosaur Encyclopaedia at Dino Russ's Lair