This famous dinosaur from the Cretaceous period was the biggest carnivorous dinosaur averaging 46 feet in length and weighing up to 7 tons. It is possible that Tyrannosaurus hunted its prey actively, but there is strong evidence that it survived by scavenging as well. It is hard to imagine such a massive creature being capable of chasing its prey over long distances. The large tail that counterbalances the head and trunk and the long legs of Tyrannosaurus gave it the ability to pursue smaller, faster prey, but only over short distances. What seems most likely is that the Tyrannosaur was a lurking predator who waited in ambush for their prey using the element of surprise to its advantage. Its small, feeble looking front legs and hands are believed to have been used either as a grappling hook for the males during mating or as an anchor for the top of the body as the animal tried to raise itself from a prone position on the ground.
TRICERATOPS
The most distinguishing feature of the Triceratops is its three facial horns and its short, solid frill protecting its neck. The head of the Triceratops is considerably larger in proportion to its body size in order to accommodate these bony structures. With such armor, it is possible that an adult Triceratops would make a formidable opponent for even the largest carnivores of the Cretaceous period. Although there are ten species of Triceratops currently recognized that are distinguished from one another by their size and general body proportions, it is possible that some of these animals are actually young individuals. Other variations could be accounted for by normal variations within a species and differences between males and females.
VELOCIRAPTOR
The Velociraptor of the late Cretaceous period is best known for its principal weapon against prey: the enormous claw on its second toe. The joints of this toe are especially enlarged so that the toe can be raised upward and backward to avoid damage while running. All of the toes could be flexed through a very wide arc to penetrate the flesh of the prey. Small animals would have been caught by the long, powerful and sharply taloned hands. By holding the prey at arms length protected the Velociraptor from being bitten. This also gave the Velociraptor room to draw up its hind leg to be kicked against the belly of the prey thereby disemboweling its prey. To overcome larger prey, the Velociraptor may have hunted in packs. Some would slow the victim down by grasping its tail and hindlegs while the others would aim lethal kicks to its underside.
DILOPHOSAURUS
The Dilophosaurus of the early Jurassic period was the earliest large carnivorous dinosaur. The two crests on the head made from two thin ridges of bone situated side by side give this animal its name which means "two-ridged reptile." The function of these tall crests still remains a mystery although it is believed that they were associated with some aspect of the behavior of the animal, perhaps visual signaling for recognition purposes. Like other carnivores, the Dilophosaurus has a large head in proportion to its body, small, weak front legs, powerful hind legs, and a long tail. Dilophosaurus was different because of its weak and slender jaws which probably could not withstand the stress of a struggling prey. It has been suggested that Dilophosaurus was a scavenger rather than an active predator.
STEGOSAURUS
Stegosaurus of the late Jurassic period gets its name, "roofed reptile" from the large bony plates found along its back which were long thought to form a protective shield from attack. It is now believed that the plates were used as radiators and solar-panels for the regulation of body temperature. When cut in sections, it was discovered that they were not hollow inside, but were similar to a honeycomb full of open spaces. This implied that the plates were supplied with blood that could either be warmed or cooled depending on whether the Stegosaurus situated itself in the sun or shade. Since Stegosaurus was a slow-moving herbivore who spent most of its time grazing on ground plants, it must have been easy prey for the large carnivores. A Stegosaur's best defense was undoubtedly its spike bearing tail. The large, sharp double pair of bone spikes could have inflicted severe injury on an attacking predator.
APATOSAURUS
The adult Apatosaurus of the Jurassic period weighed about 30 tons and measured 69 feet long. Apatosaurus is still sometimes referred by its "other" name, Brontosaurus, mistakenly because of confusion created in the early part of the century when the bones of several dinosaurs were frequently interchanged by accident. Both the fore and hind limbs are pillar-like with short toes like an elephants in order to support the weight of the animal effectively. A single clawed inner toe on the fore feet are believed to be used as defense against predators. In the event of an attack the Apatosaurus would rear up onto its hind legs using its tail as a counterbalance and defend itself with the large claws. It is also possible that they used the whip-like end of their tail as a means for self-defense.
ARCHAEOPTERYX
Since Archaeopteryx was first discovered in 1861, it has been surrounded by controversy. As recently as 1985 some scientists have expressed doubts about the authenticity of the feather impressions on the limestone surrounding the skeletons that have been found. Some have claimed that they were printed on the specimen as a hoax. In essence, Archaeopteryx is an early bird that still possessed several features from its reptilian forbearers. The wings of the Archaeopteryx are not quite the same as a birds because they still have three separate, clawed fingers; birds no longer have claws. Archaeopteryx also had short, spiky teeth and a long, bony tail like its reptile relatives where a bird has no teeth and a reduced tail to save weight.
PACHYCEPHALOSAURUS
The enormous thickened dome of bone and the knobs on the back of the skulls of Pachycephalosaurus are its most distinguishing feature. One obvious reason for this dome is as a means for attacking and running off a potential predator. It has also been suggested that, like sheep and goats, Pachycephalosaurus use head-to-head butting as a means of establishing the social hierarchy within a group, especially among the males. In most cases, the size of the head dome signaled the status of the individual; the larger the dome, the more dominant the animal. However, when similarly sized individuals met, the seniority of each would have to be decided by a head pushing or butting match.
PROTOCERATOPS
The Protoceratops was one of the earliest horned dinosaurs although there are actually no horns on their faces. Instead, the skull had a well developed neck shield and a thickened area of bone just above the eye sockets and on top of the snout where a horn would appear in later dinosaurs. Protoceratops is probably the most famous Mongolian dinosaur because of the many nests of eggs that have been discovered. Young Protoceratops have also been found as well as some babies that had not even hatched from their eggs yet. The frill of the Protoceratops is believed to be used for other reasons besides defense from predators. Much in the same way that deer and antelope use their horns to establish social order and maintain territories, the Protoceratops used their frills. The larger the frill the more dominant the individual in the social order and, hence, more attractive to the females of the species.
ALLOSAURUS
The Allosaurus of the Jurassic period was one of the most well-equipped predatory dinosaurs. The huge jaws were lined with large stabbing and cutting teeth, both for killing and dismembering their prey. The strong neck and back would have aided the jaws in tearing off huge chunks of flesh. The large claws on the hands and feet could easily subdue their prey. Allosaurus' main drawback is that its body was not built for high speed pursuits. In fact, they are believed to be large, lumbering creatures. Most likely, Allosaurus were probably scaveng
