Fig. 95.–Skeleton of Brontosaurus excelsus. × 1⁄180. (After Marsh.)
Brontosaurus excelsus of the Upper Jurassic of Wyoming was a giant at least 60 feet long and about 10 feet high. The head is extremely small in proportion, not so broad as the fourth of the thirteen vertebrae of the long and flexible neck. The trunk is comparatively short, the tail longer than the neck, and provided with numerous chevron-bones. Most of the vertebrae are hollow, especially the five co-ossified sacrals. The spinal canal of the sacral region is very wide, indicating a strong sacral swelling in conformity with the huge posterior limbs. The pubic bones are stronger than the ischia. The long axis of the former stands almost vertically like that of elephants, and the knee is scarcely bent in the erect position. The shoulder-girdle consists of long scapulae, broad at the base and small, almost square and perforated coracoids, which latter fit into a pair of partly ossified plates representing the sternum.
Atlantosaurus immanis of the Upper Jurassic of Wyoming and Colorado, is supposed to have been 115 feet long, perhaps the biggest and bulkiest of all animals, the femur measuring more than 6 feet in length and 2 in width at the upper end.
Morosaurus grandis, of the Upper Jurassic of Wyoming, with allied forms in the Purbeck and Wealden of England, reached a length of 30 feet; in general appearance resembling Brontosaurus, but the sacrum consists of four vertebrae only, and the ischia are bent backwards in their distal halves, so that their symphysis is formed by the shafts instead of by their ends.
Ornithopsis and Cetiosaurus, likewise huge creatures, from the English Wealden and from the Great Oolite respectively, are rather imperfectly known, although several species of each, under many generic synonyms, have been described.
Fig. 96.–Front view of the pelvis of Morosaurus grandis. × 1⁄30. (After Marsh.) a, First sacral vertebra; b, "transverse process" (rib) of first sacral; il, ilium; is, ischium; nc, neural canal; pb, pubis.
Fig. 97.–Skull of Diplodocus longus. × 1⁄12 (After Marsh.)