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Diplodocus longus

Whenever the longest animals are discussed, Diplodocus is sure to be named. It is among the very longest land animals to have ever lived. The length of this extraordinary animal has been put at 28-30 meters (92-100 feet) or a little more than the distance from home plate to first base on a baseball diamond. While exceptionally long, Diplodocus was a lightweight by sauropod standards, weighing in at around 10 tons. Compare this to its 50 ton cousin, Brachiosaurus. In order to reach such lengths, Diplodocus evolved a specialized, light, but strong skeleton that allowed it to raise its head much like modern crane. Current thinking among paleontologists is that Diplodocus carried its tail off the ground.

The largest dinosaurs (whether you measure them by length, weight or height) are all sauropods. While members of this diverse group are easily recognized by their distinctive long necks, long tails and small heads, there are substantial differences between many of them. The three best known groups of sauropods are diplodocids, camarasaurs and brachiosaurs. The taxonomic relationships of dinosaurs are a complicated arrangement full of long Greek and Latin words. This complex system helps us understand which dinosaurs are related to one another as well as the characteristics they have in common. The systematics of a specimen tell the story of its lineage and evolutionary relationships.

The diplodocids are the longest dinosaurs : Diplodocus (23-28 meters) from North America was the longest; Mamenchisaurus (20-22 meters) from China had the longest neck of any dinosaur; Barosaurus (23-27 meters) from Africa and North America had a long neck and shorter tail; and Apatosaurus (formerly called Brontosaurus) (18-21 meters) from North America was shorter and stockier than the others.

In an interesting development, fragmentary remains of a huge diplodocid, named Supersaurus, have been found in Colorado. Size estimates, based on the scapula , put Supersaurus at 42 meters long and maybe 50 tons. If confirmed, it would be the longest dinosaur yet found.

Diplodocids have a collection of skull characteristics that separate them from other sauropods. Thus, diplodocid heads are long and slender with pencil-shaped teeth only at the front of the mouth. They do not have any chewing teeth along the jaw. Their nostrils are located at the top of the head rather than towards the front. This arrangement (similar to elephants and tapirs) has led to speculation that they had some sort of trunk-like appendage. Gastroliths (small polished stones) often found with sauropod fossils may indicate that they had a crop, analogous to the gizzard of chickens and other birds, to help grind up the vegetation they ate.

Diplodocids are further distinguished by body shape. They were very horizontal with long necks and tails extending many feet to the front and back. In addition, their hind legs were longer than the front ones. The camarasaurs and brachiosaurs, while also having long necks and tails, had body shapes distinctly their own.

The old notion that diplodocids, and all sauropods in general, were too large to live on land and thus had an aquatic lifestyle has been shown to be wrong. There is some evidence to suggest that they traveled in groups, if not herds, and that immature animals may have lived with older animals. Sauropods prospered from the Early Jurassic right through to the end of the Cretaceous, but their zenith was during the Jurassic-Cretaceous transition, when they were the dominant herbivores.

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