Diplodocus
 

Diplodocus was a dinosaur of the Jurassic period. It lived during the Kimmeridgian (156-151 million years ago) and Tithonian (151-146 million years ago) ages. Fossils of Diplodocus have been found in Wyoming, Montana, Utahm and Colorado. The first discovery of a Diplodocus skeleton was at Como Bluff in Wyoming. Othniel C. Marsh named it Diplodocus longus. Diplodocus was an herbivore of the infraorder Sauropoda. This creature was extremely long; it had a length of at 27 m. (about 90 feet). Diplodocus had a neck that was 8 m.(26 feet) long. The tail was about 14 m. (26 feet) in length. Diplodocus had five toes on each foot. The hind legs were longer than the front ones. The chevron bones were double-beamed. [Note - Chevron bones are on the underside of the tail.] One toe on each foot had a thumb claw. It may have been used for defensive purposes.
This excerpt of Palaeos Vertebrates states some physical characteristics of Diplodocidae:

Protruding snout; small peg-like teeth confined to anterior jaw; $ tooth crowns lack grooves on outer face; ectopterygoid processes of pterygoid anterior to lacrimal, reduced and do not project ventrally

[Note - The pterygoid is a process that projects down from the sides of the sphenoid. The sphenoid is a bone that is irregular in shape. It is in front of the occipital at the base of the skull. The lacrimal foramen is the opening of the tear duct.]

This portion mentions some other key points about the anatomy:

$ 15 cervical + 10 dorsal (+1 dorsosacral) vertebrae; tall neural spines; spines cleft; 80+ caudal vertebrae with "whiplash" of unornamented long bones at end

Dipolodocus was a terrestrial animal and very likely moved in groups. It may have spent a substantial amount of time on fern prairies. However, it would not have been confined to those places. Forests would have provided ample cover for a young Diplodocus who had just hatched. He or she would have had to be concerned about predators. The young must have joined up with the adults as soon as possible.

Neal Robbins

P.S. The taxonomy of Diplodocus is:

Kingdom: Animalia
Phylum: Chordata
Class: Archosauria
Order: Saurischia
Suborder: Sauropodomorpha
Infraorder: Sauropoda
Family: Diplodocidae
Genus: Diplodocus
The species include:

Diplodocus longus
D. hayi
D. carnegiei