Dinosauria

Dinosauria (Gr., 'terrible lizards'), an important group of Mesozoic reptiles, known partly by their skeletons, partly by their footprints. They were gigantic forms, some of them at least 80 feet in length, and many of their characters lead on to birds. Thus in the hip-girdle the pubic bones were in many cases turned, not forwards as in other reptiles, but backwards as in birds; the legs were also in part bird-like; the fore-limbs were less developed than the legs; some of the bones apparently contained air-cavities, &c. Atlantosaurus (q.v.), Stegosaurus, Iguanodon (q.v.), and Megalosaurus (q.v.) are important types. They begin in Triassic strata, become very prominent in the Jurassic fanna, continue well represented in the Chalk, and then terminate. A large number have been found in America, and our knowledge of them is mainly due to the researches of Pope and Marsh. They were terrestrial animals, though some, such as Iguanodon, frequented marshy ground. Some seem to have been carnivorous, others vegetarian. The group is a large and varied one, gradually becoming more defined in its limits and characters. The relations to other fossil reptiles will be discussed under REPTILE.