Art. LIII.—Notice of New Dinosaurian Reptiles from the Jurassic formation; by Professor O. C. Marsh.
The gigantic Dinosaur, Atlantosaurus montanus, described by the writer in the July number of this Journal,[1] proves to belong to a lower horizon than at first supposed, and is really from the upper Jurassic. Additional remains of the type specimen, moreover, throw considerable light on the structure of this largest of land animals, and indicate that it is the representative of a distinct family, which may be called Atlantosauridæ.
In the type genus, Atlantosaurus, one of the most important characters is the pneumaticity of the vertebræ, as mentioned in the original description. Another noteworthy feature is the absence on the femur of a third trochanter. The shaft of the bone is somewhat thickened at the point where this process should be, but the trochanter is wanting. The size of the original specimen of A. montanus may be estimated from the femur, which was about seven feet in length. If the animal had the proportions of a Crocodile, it was at least eighty feet long.
Apatosaurus ajax, gen. et sp. nov.[2]
Another gigantic Dinosaur, allied to the above, and of scarcely less interest, is represented in the Yale Museum by a nearly complete skeleton in excellent preservation. It is from the Jurassic beds in the Eastern foot hills of the Rocky Mountains, but from a somewhat lower horizon than the type of Atlantosaurus.
The cervical vertebræ are strongly opisthocoelous, and are rendered comparatively light by large pneumatic cavities in the centra. The anterior dorsals have similar characters. The posterior lumbars have the articular faces very nearly flat, and transverse. The sacral vertebræ are more solid, and have their transverse processes nearer the middle of the centra than in Atlantosaurus. The anterior caudals are biconcave, and their
- ↑ Vol. xiv, p. 87, 1877. The name Titanosaurus was first given, but, being preoccupied, may be replaced by Atlantosaurus.
- ↑ The principal characters of this genus and its nearest allies were given by the writer in a paper before the National Academy of Science, at the meeting in New York, October 25th, 1877.
