The restoration by Mr. Knight is drawn from a very careful model made under my direction, in which the proportions of the animal are precisely estimated. It is, I think, accurate--for a restoration--as well as interesting and up-to-date. These restorations are the "working hypotheses" of our science; they express the present state of our knowledge, and, being subject to modification by future discoveries, are liable to constant change.
By contrast, the second type of giant dinosaur, the _Brontosaurus_, or "thunder saurian" of Marsh, as shown in the restoration (fig. 22), was far more massive in structure and relatively shorter in body. Five more or less complete skeletons are now to be seen in the Yale, American, Carnegie, and Field Columbian museums. In 1898 we discovered in the bluffs, about three miles west of the Bone-Cabin Quarry, the largest of these animals which has yet been found; it was worked out with great care and is now being restored and mounted complete in the American Museum. The thigh-bone is enormous, measuring five feet eight inches in length, and is relatively of greater mass than that of _Diplodocus_. The neck, chest, hips, and tail are correspondingly massive. The neck is relatively shorter, however, measuring eighteen feet, while in _Diplodocus_ it measures over twenty-one feet. The total length of this massive specimen is estimated at sixty-three feet, or from six to eight feet less than the largest "long-limbed" dinosaur. The height of the skeleton at the hips is fifteen feet. There is less direct evidence that the "thunder saurian" had the power of raising its fore quarters in the air than in the case of the "light-limbed saurian," because no bend or supporting point in the tail has been distinctly observed.
The third type of giant dinosaur is the less completely known "chambered saurian," the _Camarasaurus_ of Cope or _Morosaurus_ of Marsh, an animal more quadrupedal in gait or walking more habitually on all fours, like the great _Cetiosaurus_, or "whale saurian," discovered near Oxford, England. With its shorter tail and heavier fore limbs, it is still less probable that this animal had the power of raising the anterior part of its body from the ground. Of a related type, perhaps, is the largest dinosaur ever found; this is the _Brachiosaurus_, limb-bones of which were discovered in central Colorado in 1901 and are now preserved in the Field Columbian Museum of Chicago. Its thigh-bone is six feet eight inches in length, and its upper arm-bone, or humerus, is even slightly longer.