Velociraptor

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Saurischia

Family: Dromaeosauridae

Genus: Velociraptor

Species: Velociraptor mongoliensis

Introduction

The first Velociraptor fossil was discovered in 1924 in Mongolia, but it would be nearly 70 years later, in 1993, before the dinosaur would capture the imagination—and inspire the dread—of audiences around the globe with the release of the Steven Spielberg film Jurassic Park. In the film, Velociraptors feature prominently as vicious hunters that terrorize the human characters, playing a pivotal role in the plot. Its depiction by Spielberg, however, is not based on actual scientific facts about the species. For example, the Velociraptors that appeared in Jurassic Park were several times larger than those found as fossils and ran at significantly higher speeds than these animals actually ran.

Classification

The Linnaean system of classification was developed in the mid-1700s and classified living things according to certain shared physical characteristics. In the Linnaean system, Velociraptor is placed in the class Reptilia, along with all other reptiles and birds. Its order is Saurischia, meaning that its pubis bone, one of three bones forming the pelvis, pointed forward instead of backward (unlike dinosaurs in the order Ornithischia). Velociraptor is part of the suborder Theropoda, which includes all non-avian dinosaurs that had feathers. At the level of the family, it is considered a member of Dromaeosauridae, which also includes Troodon (Stenonychosaurus), Deinonychus, and Saurornithoides.

Scientists also use an alternate method of classifying species into groups, known as cladistics. In cladistics, species are classified according to the number of measurable physical characteristics they share, which determines whether or not they share a common ancestor. This helps scientists to determine whether or not to place them in the same “clade,” or group. Though cladistics analyses of Velociraptor may vary, it is most likely to be found grouped with such dinosaurs as Microraptor and Rahonavis in a clade known as Maniraptora, which contains the Paraves clade, comprising the Aves clade, under which birds are classified, and the dromaeosaur clade, under which raptors are classified.

As with any dynamic study in the field of science, cladistic analyses serve as hypotheses and can change over time as new specimens are discovered and as the science advances. In 2017 Matthew Baron and his colleagues posited a common ancestor for theropods, such as Velociraptor, and ornithischians, such as Stegasaurus, and proposed they be reclassified into a new clade, Ornithoscelida.

Anatomy

Velociraptor was a relatively small, bipedal dinosaur that stood about the height of a small dog and may have been able to sprint after its prey at speeds reaching 44 kilometers (27 mi) per hour over short distances. Unlike many other dromaeosaurids, Velociraptor's snout was long, rather than blunted, and its mouth was filled with sharp teeth—each roughly triangular in shape, with fine serrations along both edges. The dinosaur had relatively short forelimbs, stocky, muscular hind limbs, and a large, hyperextensible, sharp-tipped claw that curved out from the second digit of each hand and foot (a feature it shared with the other members of the family Dromaeosauridae). Velociraptor also had a long tail stiffened by ossified tendons that enabled it to use its tail for balance.

The 2007 discovery of quill knobs, or places where feathers attach to bone, on the forearm of a Velociraptor indicated that the dinosaur had feathers on its forelimbs and may have had a covering of feathers over its entire body. Though Velociraptor was incapable of flight or gliding, its feathers may have helped it regulate temperature or attract mates. Prior to this discovery, scientists had believed that Velociraptor, like most other non-avian dinosaurs, was covered in scales of some kind.

Intelligence

Like other dromaeosaurids, Velociraptor had a relatively large brain case for its size, and was therefore probably among the most intelligent of dinosaurs. In fact, according to James Allen Hopson, a paleontologist from the University of Chicago who has researched the brain casts of many different extinct species, dromaeosaurids like Velociraptor had EQs of 5.8—the maximum figure Hopson calculated for any dinosaur. In comparison, stegosaurs and ankylosaurs, for instance, had EQs of less than 1.

Reproduction and Population

Because scientists believe that Velociraptor shared a common ancestor with modern birds, it is not surprising that, like birds, these dinosaurs are thought to have laid their eggs in nests that remained open to the elements, then brooded (sat on) them to keep them warm and hatch them. Based on fossil evidence showing differences in the teeth of adult Velociraptors as compared to babies of the same species, paleontologists also believe that the dinosaur's diet changed over the course of its lifetime, something which may indicate the fact that young Velociraptors, like young birds today, relied on their parents for food.

One notable discovery has fascinated scientists for years. In a nest belonging to an Oviraptor, a theropod that lived during the same time as Velociraptor, researchers uncovered both Oviraptor eggs and the tiny skulls of two very young dinosaurs believed to be Velociraptors. There are several theoretical explanations for this finding, including the possibility that the young dinosaurs may have hatched from eggs that adult Velociraptors laid in the Oviraptor nest, taking advantage of the warmth and safety provided by the unknowing “surrogate parents.” (Organisms that do this are known as brood parasites, and the practice is seen in contemporary cuckoos.) The presence of the skulls could also indicate that the young Velociraptors had been eaten by Oviraptors, or vice versa.

Diet

Velociraptor was a carnivore that hunted other animals for food. Its prey is likely to have included terrestrial vertebrates, such as lizards and other small dinosaurs. One striking fossil find is that of a Velociraptor and a Protoceratops, a small dinosaur that ran on four legs and had a bony frill on its neck, locked in what appears to be a deadly fight, with the Velociraptor grabbing the Protoceratops in its claws. This fossil evidence provides at least some information regarding this predator's preferred prey. In addition, fossil evidence, such as the discovery of the skulls of Velociraptor babies in an Oviraptor nest, may mean that the stolen eggs of other reptiles constituted a portion of its diet.

Behavior

In popular literature and art, Velociraptor is often depicted as hunting prey in small packs, as do modern wild dogs in Africa. To date, there has been no specific record of a Velociraptor trackway, or set of fossilized dinosaur footprints indicating group travel. Trackways made by related species, such as Velociraptorichnus sichuanensis, have been found, suggesting that Velociraptor may have also been a social dinosaur that behaved gregariously at least part of the time. Alternatively, the presence of multiple Velociraptor remains in the same bone bed could indicate scavenging, flocking, or having been buried together by natural occurrences, such as flooding or quicksand.

Habitat and Other Life Forms

Velociraptor lived in what is now Mongolia and China during the Late Cretaceous period. The globe as a whole was significantly warmer than it is now, with even the poles being mostly free of ice. The region where Velociraptor lived was largely arid and desert-like, covered with shifting sand dunes. Other dinosaurs that coexisted with Velociraptor in the same area included the small, stocky quadruped Protoceratops, the huge herbivore Therizinosaurus, which may have used its impressive claws to drag leaves closer to its mouth, and the hulking theropod Tarbosaurus, a smaller relative of Tyrannosaurus rex. Many insects, including bees, grasshoppers, ants, and butterflies, had also appeared by this time.

Research

It was long assumed that the long, curved claws on the second digit of each of Velociraptor's fore and hind limbs served as deadly tools for tearing apart its prey. Later studies based on mechanical testing have suggested that these claws were actually ill-suited for tearing and cutting, not being sharp enough to disembowel or rip thick hides. Instead, as its claws were more akin to grappling hooks, Velociraptor may have used them to first stab and then lock itself into its prey, preventing it from escaping. The claws may even have been strong enough to support its weight while climbing, a hypothesis that lends weight to the theory that the first birds evolved from dinosaur ancestors, such as Microraptor (an earlier relation of Velociraptor) that glided down from treetops.

In a 2011 Science paper, researchers Lars Schmitz and Ryosuke Motani concluded that Velociraptor was likely a nocturnal animal, much like most modern carnivorous mammals are. A wide sclerotic ring in the eye, as found in Velociraptor, would allow more light into the eye and is predictive of nighttime activity in modern animals.

Spectroscopic analyses of fossilized proteins conducted in the late 2010s has suggested that the speedy Velociraptor relative Deinonychus may have had the faster metabolism associated with warm-blooded animals.

Bibliography

Farlow, James Orville. Complete Dinosaur. Indiana UP, 2000.

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

Li Rihui, et al. “Behavioral and Faunal Implications of Early Cretaceous Deinonychosaur Trackways from China.” Naturwissenschaften, vol. 95, no. 3, 2008, pp. 185–91.

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

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

Paul, Gregory S. Scientific American Book of Dinosaurs. St. Martin's Press, 2003.

Schmitz, L., and R. Motani. “Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology.” Science, vol. 332, no. 6030, 14 Apr. 2011, pp. 705–8, doi:10.1126/science.1200043. Accessed 25 Mar. 2020. ‌

UCMP. University of California Museum of Paleontology, 2020, www.ucmp.berkeley.edu. Accessed 20 Mar. 2020.