Overall, each dinosaur had a skeleton made up of the same basic structures: the skull, spine, ribs, shoulders, hips, legs, and tail. But individual dinosaur fossil bones do have structural differences. This is apparently dependent on several factors, including where the bones were located in the dinosaur, the bone’s purpose or purposes, and the species of dinosaur. In general, dinosaurs that depended on speed needed long, light bones, while larger, slower-moving dinosaurs needed strong, solid bones.

Some of the best examples of the differences between dinosaur bone structures are seen in the bipedal and quadrupedal herbivores. The large, heavy sauropods walked on all fours; they needed strong legs to support their enormous weight, so their bones were huge and solid. The smaller, fast-running bipedal herbivores like Dryosaurus needed to be fast; thus, they had long, thin-walled bones. These bones were essentially hollow tubes, and the insides were filled with a light bone marrow. This gave them a strong, flexible, but light-weight, structure, enabling them to move swiftly when circumstances demanded it—such as running from a predator.