Animalia Life

Velociraptors are represented by the genus Velociraptor ("speedy predator"), which is one of a group of human-sized theropods or carnivorous dinosaurs that existed during the Cretaceous in North America and Asia. Theropods include all dinosaurian carnivores and are allied to the sauropods, very large, long-necked herbivores, in a major group of dinosaurs called the Saurischia. These dinosaurs are all characterized by the forward projection of the pubis, which separates them from the other major group, the Ornithischia, in which the pubis is directed backward. Velociraptors are most closely related to a group of similar predators that includes the dromaeosaur Deinonychus, which is extremely well known from articulated skeletons found in Montana andWyoming, described by Yale University's John Ostrom in the late 1960's and early 1970's. One result of cladistic analysis of the relationships of this group is that they have been shown to be the closest relatives of Archaeopteryx, the earliest known bird. Archaeopteryx is known only from the latest Jurassic, and the dromaeosaurs are entirely Cretaceous, so it has been suggested that either dromaeosaurs represent a group of secondarily flightless birds, or alternatively that ancestral forms in the Jurassic await discovery.

Anatomy and Life Habits
The velociraptor Deinonychus ("terrible claw") is the best-known genus of this group and is thus often used as a typical example. It has an elongated, lightly built skull with numerous backwardcurving, serrated teeth, and a relatively large brain. There are large openings in the side of the skull for the eyes and for jaw muscles, which suggest a sharp-eyed predator with a fearsome bite. The neck was quite slender and flexible in contrast to the back and tail, which were fairly stiff due to the presence of ligaments and (in the tail) bony rods that provided support to the vertebral column. The arms were unusually long, and the threefingered hands bore long, sharp claws. The hind leg is particularly interesting, as the relatively short femur (upper leg bone) indicates a fastrunning animal while the second toe is modified to form a large, sickle-shaped claw that must have been held above the ground during locomotion. These anatomical features suggest that Deinonychus (and other velociraptors) was a nimble predator that was able to grasp its prey and dispatch it with lethal kicks from its sickle-claw. The femur has a special process on it for the attachment of a muscle that would have allowed a very powerful backward and downward kick, enabling effective use of the claw. Additionally, the tail is flexible near the body but stiffened by bony rods more distally, which would have made it ideal as a balancing organ. The only actual evidence of velociraptor predation comes from a specimen of Velociraptor from Mongolia, in which the individual is interlocked with the skeleton of a small Protoceratops (a herbivore), suggesting that they died in mutual combat. The most common herbivores found with Deinonychus remains are ornithopods, large, bipedal animals that would have been too large for attack by a solitary individual. This has been used as the basis for the hypothesis that velociraptors might have attacked in packs, which in turn suggests a level of organization not usually present in reptiles. The active and agile lifestyle of velociraptors, together with the possibility of group behavior in hunting, have been advanced as evidence that they had an endothermic metabolism, similar to that of modern mammals, in which internal temperature was controlled by food intake. As dinosaurs are reptiles, they had been thought to have an ectothermic metabolism similar to that of modern reptiles. Velociraptors have become well-known dinosaurs due to their role in the film Jurassic Park (1993), where they are depicted as intelligent and warm-blooded, in contrast to the long-held perception of dinosaurs as ponderous and slow-witted animals.

Velociraptor Facts

Classification:
Kingdom: Animalia
Subkingdom: Bilateria
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Saurischia
Suborder: Dromaeosaurida (medium-sized carnivores with an enormous claw on the second toe of the hind foot)
Geographical location: North America and Asia
Habitat: Terrestrial habitats
Gestational period: Unknown
Life span: Unknown
Special anatomy: Medium-sized bipedal carnivores with a well-developed, sickle-shaped claw on the hind foot

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