Dinosaur

The distinguishing characteristics of the dinosaurs include the structure of their skull and other bones. Dinosaurs typically had 25 vertebrae, plus three vertebrae that were fused to form their pelvic bones. The dinosaurs displayed an enormous range of forms and functions, however, and they filled a wide array of ecological niches. Some of the dinosaurs were, in fact, quite bizarre in their shape and, undoubtedly, their behavior.

The smallest dinosaurs were chicken-like carnivores that were only about 1 ft (30 cm) long and weighed 5-6 lb (2-3 kg). The largest dinosaurs reached a length of over 100 ft (30 m) and weighed 80 tons (73 metric tons) or more—more than any other terrestrial animal has ever achieved. The largest blue whales can weigh more than this, about 110 tons (100 metric tons), representing the largest animals ever to occur on Earth. The weight of these aquatic animals is partially buoyed by the water that they live in; whales do not have to fully support their immense weight against the forces of gravity, as the dinosaurs did. When compared with the largest living land animal, the African elephant, which weighs as much as 7.5 tons (6.8 metric tons), the large species of dinosaurs were enormous creatures.

Most species of dinosaurs had long tails and long necks, but this was not the case for all species. Most of the dinosaurs walked on all four legs, although some species were bipedal, using only their rear legs for locomotion. Their forelegs were greatly reduced in size and probably were used only for grasping. The tetrapods that walked on four legs were all peaceful herbivores. In contrast, many of the bipedal dinosaurs were fast-running predators.

The teeth of dinosaur species were highly diverse. Many species were exclusively herbivorous, and their teeth were correspondingly adapted for cutting and grinding vegetation. Other dinosaurs were fierce predators, and their teeth were shaped like serrated knives, which seized and stabbed their prey and cut it into smaller pieces that could be swallowed whole.

Until recently, it was widely believed that dinosaurs were rather stupid, slow-moving, cold-blooded (or poikilothermic) creatures. Some scientists now believe, however, that dinosaurs were intelligent, social, quick-moving, and probably warm-blooded (or homoiothermic) animals. This is a controversial topic, and scientific consensus has not been reached on whether or not some of the dinosaurs were able to regulate their body temperature by producing heat through metabolic reactions. It is absolutely undeniable that dinosaurs were extremely capable animals. This should not be a surprise to us, considering the remarkable evolutionary successes that they attained.