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Dinosaurs Adapted. The presence of ripple marks, for example, indicates a shallow-water environment.
Fossil plants indicate something about climate. Associated animal remains like turtle, crocodile, or fish scales
point to a nearby aquatic environment. Whatever habitat is inferred from clues like these, however, one must
keep in mind that it is only an inference and does not necessarily reflect the actual living conditions of the
Dinosaur in question. Rather, such clues reflect the animal's death environment or burial situation. The condition
of the skeleton and its bones and their degree of disarticulation help to reveal the extent of preburial transport.
Accordingly, certain groups of dinosaurs, such as the ornithopods, included a succession of types that were increasingly adapted for efficient food processing. At the peak of the ornithopod lineage, the hadrosaurs (duck-billed Dinosaur of the Late Cretaceous) featured large dental batteries, in both upper and lower jaws, consisting of many tightly compressed teeth that formed a long crushing or grinding surface. The preferred food of the duckbills cannot be certified, but at least one specimen found in Wyoming offers an intriguing clue: fossil plant remains in the stomach region have been identified as pine needles. Other Late Cretaceous contemporaries, the ceratopsians (horned dinosaurs), had similarly compacted teeth, forming solid dental batteries that consisted of dozens of teeth. But here the upper and lower batteries occluded in serrated shearing blades rather than crushing or grinding surfaces. Ordinarily, slicing teeth are found only in flesh-eating animals, but the bulky body and the unclawed, hooflike feet of Dinosaur like Triceratops clearly are those of plant eaters. The sharp beaks and specialized shearing dentition of the ceratopsians suggest that they probably fed on tough, fibrous plant tissues, perhaps palm or cycad fronds. The giant sauropods like Diplodocus and Apatosaurus must have required large quantities of plant food, but there is no direct evidence as to the particular plants they preferred. Since angiosperms rich in calories and proteins did not exist during most of the Mesozoic, it must be assumed that these sauropods fed on the abundant conifers and palm trees. Such a cellulose-heavy diet would have required an unusual bacterial flora in the intestines to break down the fibrous tissues. A digestive tract with one or more crop chambers containing millstone batteries might have aided in the food-pulverizing process, but such gastroliths, or ³stomach stones,² have only rarely been found in association with any Dinosaur skeleton (the Seismosaurus specimen and its several hundred such stones is an important exception). The food preference of herbivorous Dinosaur can be inferred to some extent from their general body plan as well as the form of their teeth. It is probable, for example, that low-built animals like the ankylosaurs, stegosaurs, and ceratopsians fed on low shrubbery (but not grasses, which had not yet appeared). The tall ornithopods, especially the duckbills, and the long-necked sauropods probably browsed on high branches and treetops. The flesh-eating Dinosaur must have eaten anything they could catch, since predation is a highly opportunistic lifestyle. In several instances the prey victim of a particular carnivore has been established beyond much doubt. Remains of the small predator Compsognathus were found containing a tiny skeleton of the lizard Bavarisaurus in its stomach region. In Mongolia two different Dinosaur skeletons were found together, a nearly adult-size Protoceratops in the clutches of its predator Velociraptor. Two of the many skeletons of Coelophysis discovered at Ghost Ranch in New Mexico contained bones of several half-grown Coelophysis, apparently an early Mesozoic example of cannibalism. The skeletons of Deinonychus unearthed in Montana were mixed with fragmentary bones of a much larger victim, the herbivore Tenontosaurus. This last example is significant because the multiple remains of the predator Deinonychus associated with the bones of a single large prey animal, Tenontosaurus, strongly suggests that Deinonychus hunted in packs. Herding behavior That Deinonychus was a social animal should not come as a surprise. Many animals today are gregarious and form groups. Fossil evidence documents similar herding behaviour in a variety of dinosaurs. The mass grave in Bernissart, Belg., held a large assembly of Iguanodon. The dozens of skeletons of Coelophysis of all ages recovered in New Mexico indicate group association and activity. The many specimens of Allosaurus at the Cleveland-Lloyd Quarry in Utah may denote a herd of animals attracted to the site for the common purpose of scavenging. These rare multiple occurrences of skeletal remains have repeatedly been reinforced by Dinosaur footprints that register herding habits. First noted by Roland T. Bird in the early 1940s, a series of large, basin-size depressions along the Paluxy riverbed in central Texas proved to be a succession of giant sauropod footsteps preserved in the Early Cretaceous limestone of the region. Bird noticed that there were many trackways and that they were nearly parallel and progressed in the same direction. He concluded that ³all were headed toward a common objective² and suggested that the sauropod track-makers ³passed in a single herd.² Large trackway sites are known in the eastern and western United States, Canada, Australia, England, Argentina, South Africa, China, and other places. These sites, ranging in time from the Late Triassic to the latest part of the Cretaceous, document herding as common behaviour among a variety of Dinosaur types. Some Dinosaur trackways register hundreds, perhaps even thousands, of animals, possibly recording mass migrations. They suggest the presence of great populations of sauropods, prosauropods, ornithopods, and probably most other kinds of dinosaurs. The majority must have been herbivores, and many of them were huge, weighing several tons or more. The impact of such large herds on the plant life of the time must have been devastating. Growth and life span
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