Oviraptor

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Saurischia

Family: Oviraptoridae

Genus: Oviraptor

Species: Oviraptor philoceratops

Introduction

The discovery of the first specimen of Oviraptor was particularly significant. In 1923, a Gobi Desert fossil hunt undertaken by scientists from the American Museum of Natural History discovered the world's first positively identified dinosaur eggs.

Oviraptor, a long-legged, small theropod, lived in central Asia during the Late Cretaceous period (99–66 million years ago). This species was very successful; however, the K/T (or (P/T) extinction event, which occurred between the Cretaceous and the Tertiary (Paleogene) periods some 66 million years ago, was responsible for its extinction. A great deal of debate surrounds the reasons for this mass extinction event, responsible for wiping out all dinosaurs and 50 percent of all other life. Current theory states that extinction was likely caused by a combination of reasons: meteoric impact, sea regression, volcanism, and climate change.

Classification

Scientists use two primary methods to organize animals into different groups. Linnaean taxonomy, also called “systematics,” groups organisms in a hierarchical fashion according to overall physical similarity, while an alternate, more dynamic system called “cladistics” attempts to create groups that better reflect the evolutionary relationships between species. The more shared evolutionary novelties they have, the more likely it is that they also share a common ancestor, placing them in the same clade.

Currently, dinosaur classification groups dinosaur species in one of two orders: the Ornithischia (or bird-hipped dinosaurs) or the Saurischia (or lizard-hipped dinosaurs). Somewhat confusingly, it is from the lizard-hipped dinosaurs that modern day birds evolved, which represents an example of convergent evolution, whereby the backward pointing pubis seen in ornithischian dinosaurs and birds actually evolved separately..

The large herbivorous Sauropoda species and the predominately carnivorous Theropoda species are the two major groups, or suborders, of the Saurischia order. In 2017 Matthew Baron and his colleagues proposed a new order, Ornithoscelida, encompassing both the theropods and the ornithischians.

The bipedal theropods, which include Oviraptor, were the most diverse and oldest dinosaur species to have ever existed, first appearing during the Late Triassic period about 230 million years ago and surviving until the end of the age of dinosaurs about 66 million years ago.

The theropods comprise a number of clades, including the Tetanurae and its two main divisions, the Carnosauria and the Coelurosauria. Oviraptor species belong to the coelurosaurs, which contain intelligent and fast-running bipedal carnivores that have more in common with birds than carnosaurs, and include other species such as the famous Tyrannosaurus. The Oviraptoridae family generally consists of species that are avian-like in appearance with beaked mouths and probable feathers. It includes Oviraptor and close relatives such as Conchoraptor and Ingenia.

Anatomy

With its feathers, large tooth-less beak, and long claws, Oviraptor was decidedly avian in appearance. One of its most notable features was its bird-like toothless beak and distinctive crest on its head. Its beak was very strong and thought to be capable of great crushing strength. It is also thought that the head crest may have been a sexual characteristic and larger in males than in females, demonstrating possible sexual dimorphism.

Oviraptor was not large a large species by dinosaur standards, with a body length of about 2 to 2.5 meters (6 to 8 feet) and a weight between 25 to 35 kilograms (55 and 75 pounds). Its skeleton was lightly built, and its overall body shape followed that of all theropod species. Possessing long and lightly-built hind legs, Oviraptor was a bipedal dinosaur and probably one of the fastest dinosaur species to have existed. Some scientists even claim it could have reached speeds of up to 70 kilometers (43 miles) per hour. Its legs were very strong and ended with three-toed claws on each foot. It had a relatively long neck and tail, and while its forearms were short, they were very strong and ended in three-digit hands with long, curved claws.

Intelligence

The most often used technique to measure and compare intelligence in animal species is the encephalization quotient (EQ), calculated as a body size to brain size ratio. This figure can reach up to 5.8 in dinosaurs; however, most dinosaurs fall within a range of 0.1 to 2.0 on a scale that extends to an upper limit of 8.0, the approximate value calculated for the human brain. Though this figure compares poorly to most modern-day animals, there is growing evidence that dinosaurs may have been more intelligent than first thought.

Oviraptor is among the most intelligent of dinosaur species. Although they had an EQ score falling between 1.0 to 1.9, it is considered likely that they were at the higher end of this range.

Reproduction and Population

One of the difficulties for paleontologists is determining past behavior from fossilized remains. To date, no incontrovertible evidence has been uncovered supporting highly developed or sophisticated parental care among dinosaurs. However, fossil finds from dinosaur nests, communal nesting grounds, and juvenile morphology have hinted strongly at the possibility of advanced parenting behavior.

Most unearthed dinosaur eggs have been empty shells that provide little insight into the species that laid them or the offspring that hatched from them, but Oviraptor is a notable exception. This species was first discovered in 1923 with what was thought to be a fossilized nest ofProtoceratops eggs buried in Mongolia's Gobi Desert. It was initially assumed that the dinosaur was preserved in the act of egg-stealing—hence its name, Oviraptor. Later discoveries of Oviraptor eggs (positively identified by the preserved embryos inside) cast doubt on the original findings and assumptions. Scientists now believe that the original eggs were actually from Oviraptor and that the remains were that of a mother brooding her own eggs, rather than a thief stealing the eggs of another species. This is one of the very few fossil find examples that provide strong evidence of brooding behavior in dinosaur species.

Diet

Unusual for a dinosaur species, Oviraptor was neither a true carnivore nor true herbivore. Classified, in fact, as an omnivore, Oviraptor consumed a varied diet of insects, meat, eggs, seeds, and plants.

Historically, Oviraptor was classified as a predominant egg-eater due to its initial discovery with a nest of fossilized eggs. Numerous paleontologists also believed that the shape of its toothless beak-like mouth would have functioned as an effective tool for breaking eggs. More recently, however, new evidence has suggested that the structure of the beak may have been more suited to a mollusk-dominated diet, with Oviraptor feeding on the clams and other shelled species that shared its environment.

This is also supported by the fact that scientists now believe that the original remains of Oviraptor were not that of an egg-thief caught in the act, but of a mother brooding her own eggs. This new evidence has researchers doubting the historical assumption that Oviraptor was a predominant egg-eater. Moreover, the discovery of Oviraptor remains with a lizard species in its stomach has certainly provided clues that this species was carnivorous to some degree.

Behavior

Not only bird-like in appearance, with a toothless beak and crested head, the Oviraptor is now also notable for exhibiting brooding behavior that strongly mimics that of birds and is one of the very few dinosaurs found that definitely demonstrates advanced parental care.

One of the current debates in paleontology is the function of anatomical structures such as the head crests present on species such as Oviraptor. Similar to other dinosaurs, it is considered likely that these features were related to sexual behavior and used to attract or signal mates regarding reproductive status or fitness.

Habitat and Other Life Forms

Although the Late Cretaceous period was generally characterized by a cooling climate, without the existence of polar ice caps, it was warmer than today. The climate has, in fact, often been described as a “greenhouse climate” with little change in the thermal gradient from the equator to the poles. While many areas of the world were still dominated by gymnosperm vegetation, the Late Cretaceous was also characterized by the arrival of grass species and the rapid radiation and diversification of angiosperms.

The Gobi basin was formed during the Jurassic period (201–145 million years ago), many millions of years after the collision between Siberia and north China. This inland basin, created many hundreds of kilometers from the ocean, was formed through a geological process known as subduction, in which the Pacific Ocean floor moved under the Asian landmass. While this basin region was primarily arid during the Late Cretaceous, it also possessed marshes and water holes created from water run-off from the nearby mountain ranges.

The semi-arid local environment was composed of sand dunes covered with a variety of plants and a constant supply of water from mountain run-off. It was the existence of these conditions that allowed for and supported the wide diversity of life forms that existed in the Gobi basin, including dromaeosaurid, saurornithoidid, and oviraptorid dinosaurs, mammals, and lizards. In particular, dinosaur species that have been unearthed with the same Mongolian Djadochta Formation as Oviraptor include the famous Velociraptor and Protoceratops species. The Djadochta Formation is also renowned for the discovery of the first dinosaur eggs ever found.

Research

Oviraptor was first discovered by George Olsen from the American Museum of Natural History on a Mongolian expedition in 1923. The partial remains were found in the Djadochta Formation of Ömnögov, Mongolia, in a southern area of the Gobi Desert, and were named based on the assumption that the species was an “egg-thief.” To date, only one species has been unearthed, although later finds in the 1980s and 1990s demonstrated that the initial discovery was not a thief caught in the act of stealing eggs, but that of a mother protecting or brooding her own eggs.

The discovery of Oviraptor has been hailed as one of the most significant in the history of paleontological study, as it provides proof that some species of dinosaur, at least, displayed advanced parental care that more strongly mimics that of modern-day birds than modern-day reptiles.

By 2019 seven such nests topped with adult oviraptorids had been discovered in the Gobi and a number without adult remains in China. Such clutches showed oviraptorids laid or arranged their eggs in overlapping circles, partly buried and with the blunt ends face up. Oviraptorid eggs may have been a blue-green color, based on chemical analyses of color pigments in shell fragments. That coloration might have aided in camouflaging the animals' open ground nests, the first among dinosaurs, which usually dug underground nests. In modern birds, blue-green eggshells are linked to paternal care, which researchers hypothesized might have originated much earlier with oviraptorids.

Through computer modeling and comparison with both living birds and lizards, researchers determined Oviraptor had a short, flexible, muscular tail with a peacock-like fan at its tip that could have been shaken to attract a mate.

Bibliography

“Bird-Like Dinosaurs.” Australian Museum, 19 Mar. 2020, australianmuseum.net.au/learn/dinosaurs/bird-like-dinosaurs. Accessed 5 May 2020.

Carpenter, Kenneth, editor. The Carnivorous Dinosaurs. Indiana UP, 2005.

Carpenter, Kenneth. Eggs, Nests and Baby Dinosaurs: A Look at Dinosaur Reproduction. Indiana UP, 1999.

Department of Palebiology, Smithsonian National Museum of Natural History. Smithsonian Institution, www.paleobiology.si.edu. Accessed 5 May 2020.

Dinobase. University of Bristol, dinobase.gly.bris.ac.uk. Accessed Apr. 2010.

“The Dino Directory.” Natural History Museum, www.nhm.ac.uk/jdsml/nature-online/dino-directory. Accessed 5 May 2020.

Drake, Nadia. “Dinosaurs May Have Shaken Their Tail Feathers to Woo Mates.” Wired, 4 Jan. 2013, www.wired.com/2013/01/dinosaur-courtship-feathers. Accessed 6 May 2020. ‌

Fastovsky, David E., and David B. Weishampel. Dinosaurs: A Concise Natural History. 3rd ed., Cambridge UP, 2016.

Fastovsky, David E., and David B. Weishampel. Evolution and Extinction of the Dinosaurs. 2nd ed., Cambridge UP, 2007.

Hopson, James A. “Relative Brain Size and Behavior in Archosaurian Reptiles.” Annual Review of Ecology and Systematics, vol. 8, 1977, pp. 429–48.

Jerison, H. J. “Brain Evolution and Dinosaur Brains.” American Naturalist, vol. 103, no. 934, Nov.–Dec. 1969, pp. 575–88.

Lucas, Spencer G. Dinosaurs: The Textbook. 6th ed., Columbia UP, 2016.

Martin, Anthony J. Introduction to the Study of Dinosaurs. 2nd ed., Blackwell, 2006.

Meijer, Hanneke. “Duck Egg Blue and Oviraptor Green: Study Reconstructs Colour of Dinosaur Eggs.” The Guardian, 11 Oct. 2017, www.theguardian.com/science/2017/oct/11/duck-egg-blue-and-oviraptor-green-study-reconstructs-colour-of-dinosaur-eggs. Accessed 6 May 2020. ‌

Norell, Mark, et al. Discovering Dinosaurs: Evolution, Extinction, and the Lessons of Prehistory. Updated and revised ed., U of California P, 2000.

“The Oviraptoridae (‘Egg Snatchers’).” UCMP. University of California Museum of Paleontology, 2020, www.ucmp.berkeley.edu/diapsids/saurischia/oviraptoridae.html. Accessed 5 May 2020.

Parker, Steve. Dinosaurus: The Complete Guide to Dinosaurs. 2nd ed., Firefly Books, 2016.

Weishampel, David B., et al, editors. The Dinosauria. 3rd ed., U of California P, 2007.

Willis, K. J., and J. C. McElwain. The Evolution of Plants. 2nd ed., Oxford UP, 2014.