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Diplodocus

Diplodocus was one of those gigantic sauropod dinosaurs moving at the speed of a turtle. This dinosaur is the longest to have existed and an adult specimen could measure more than 175 feet from the tip of its muzzle to the end of its tail. In comparison, a university football field is 300 feet long and a school bus measures 40 feet from bumper to bumper. An adult Diplodocus would cover the entire space between the goal line of one team and the 40-yard line on the other. These are absolutely ridiculous dimensions! Most of its length came from its extremely long neck.

“Double beam"

This sauropod herbivorous dinosaur of the diplodicids family lived during the Upper Jurassic era, about 150 million years ago, in the regions of the current american midwest. The name Diplodocus, which means "double beam", refers to the chevrons (bones) on the underside of its tail. In other dinosaurs, they have the shape of a V; in Diplodocus, they have the shape of a protruding T in the front and the back. The Diplodocus is very easily recognizable by its appearance which is typical of large sauropods; his neck and tail are very long, his head is very small and looks much like that of a horse and his four legs are short and sturdy.

Diplodocus was rather slender

Although Diplodocus was the largest, it was not the heaviest. Relative to the other sauropods of the Upper Jurassic period, it was rather slender. Unlike Brachiosaur, which exceeded 50 tons, Diplodocus only showed 20 or 25 tons on the scale. However, it is not excluded that some very old individuals could reach a weight between 30 and 50 tons. But this is nothing compared to the sauropod Seismosaurus whose size of more than 100 tons could literally cause earthquakes and landslides. Moreover, there is still debate as to whether Seismosaurus was in fact a very large species of Diplodocus: D. hallorum.

Three species of Diplodocus

Today, there are 3 species of Diplodocus officially recognized by paleontologists:

  • Diplodocus longus (D. longus)
  • Diplodocus carnegii (D. carnegii)
  • Diplodocus hallorum (D. hallorum)

Longer back legs

Unlike Brachiosaurus which had longer front legs, in Diplodocus it is the hind legs that were longer. This means that his hips were higher than his shoulders and his back was leaning forward. A very large part of this creature's length comes from its neck and tail which were very similar in structure. The long neck of this dinosaur was riding on a scaffold of about 15 elongated vertebrae while its tail was made of 80 much shorter and flexible bones. This particular skeletal arrangement suggests that Diplodocus not only used its tail to counterbalance the weight of its neck but also as a defense weapon to repel the attacks of predators of the time. His tail could play the role of soft whip although no fossil evidence officially bears this out. But given its enormous size, it is rather unlikely that a 25-tons adult specimen would have been the target of predators even though Allosaurus (which weighed 1 ton) was smart enough to pack. Rather, the theropod dinosaurs of the Upper Jurassic North America would have targeted the eggs, hatchlings and juveniles of this sauropod and attacked an adult only if it was sick or in his old age.

Little brain

The sauropods, like Diplodocus, possessed an infinitely small brain relative to the rest of their bodies; much smaller than that of carnivorous dinosaurs. This dinosaur was scarcely more intelligent than the plants he ate. If he wandered in herds like some experts think then his quotient might be slightly higher. But still, Diplodocus was an Albert Einstein of the Jurassic in comparison with the herbivorous dinosaur Stegosaurus whose brain size equaled that of a peanut.

Nostrils in the forehead

Diplodocus skull

Strangely, the nasal openings of this dinosaur, like many other sauropods, are well above its forehead rather than at the tip of its snout. At one point researchers thought that Diplodocus might have a trunk. After comparing with the skulls of elephants they however rejected this theory. Another common thesis is that this dinosaur required this adaptation in order to live in the water. But the sauropods' bodies were not well adapted to aquatic life because they had pockets of air that would have made them too floating and unstable in deep water. To this day there is no satisfactory explanation to justify the strange disposition of the nasal cavities of the sauropods.

Claw on the big toe

Diplodocus claw

Like humans, Diplodocus had wide feet with 5 toes. The big toe, however, had an exceptionally large claw. Like the nasal fossae, the utility of the claw is not known. One can speculate that they are vestiges of evolution and that at some point in the lineage their ancestors really needed it.

Rapid growth

Diplodocus vs human
Debivort - Wikimedia commons

Like other sauropods, Diplodocus grew very rapidly and reached sexual maturity at about 10 years of age. It continued to grow all his life. Due to its colossal size, the life expectancy of this creature could extend up to 100 years.

Posture

Dippy the Diplodocus
Dippy the Diplodocus

Paleontologists have a hard time reconciling the idea that the sauropod dinosaurs kept their head and neck high in the air with the fact that they possessed a cold-blooded metabolism. Such a posture would have placed enormous stress on the hearts of these animals if it constantly had to pump dozens of gallons of blood 40 feet into the air. The burden of proof shows that Diplodocus rather kept his neck parallel to the ground in a horizontal position. Scientists now believe that ligaments running his entire body from the base of the skull to the hips allowed this dinosaur to keep his neck in a stable horizontal position without having to use his muscles. The vertebrae are divided in the middle leaving enough space for this kind of ligaments to attached to it.

Food and digestion

Diplodocus was herbivorous and fed mainly on vegetation. In search of leaves, he could stand on his hind legs to reach the top of the trees. However, the opinion of some experts is that because of the size and structure of his body, the animal certainly could not hold the pose very long. It is therefore likely that the sauropod would stand up only for a very short time to bring down the trees and then fed on the leaves closest to the ground. Another theory often argued is that the animal's neck was extremely flexible allowing it to reach both the high vegetation and the low vegetation without having to move the rest of its body.

This sauropod had a number of small, forward-looking teeth that looked like stakes and were placed on the front of his mouth. These teeth were thin and delicate and frequently had to be replaced. The high frequency of replacement in Diplodocus suggests that it fed on abrasive vegetation such as soft plants containing silica or gravel-covered plants on the soil.

Research and modeling experiments, however, have shown that the bite force of this dinosaur was relatively weak and that it tended to make horizontal movements of gliding when chewing food. The jaw of Diplodocus was therefore better adapted to the consumption of ferns, conifers, shrubs, moss and soft leaves that it tore from trees. And rather than chewing, this dinosaur spent considerable time fermenting its food in his enlarged intestine until the nutrients were extracted and absorbed by his body; the rocks not helping digestion at all.

Reproduction and nests

Although there is no direct evidence that Diplodocus erected nests, nest sites have been associated with other sauropods such as the titanosaur Saltasaurus. These nests of titanosaurs may make us believe that these dinosaurs commonly lay their eggs on a large surface in many shallow pits, each covered with vegetation. In Diplodocus and other sauropods, the size of the eggs and individual eggs was relatively small for such large creatures. Larger eggs required longer incubation time, which increased the risk of predator feeding on them before they could hatch.

Fossils

Diplodocus, Carnegie Museum of Natural History
Diplodocus, Carnegie Museum of Natural History

The earliest remains of this sauropod were discovered in 1877 in Cañon City, Colorado by Benjamin Mudge and Samuel Wendell Williston. The following year, the famous paleontologist Othniel Charles Marsh named the Diplodocus specimen. Since then, a large number of fossils of this dinosaur have been dug up at the Morrison Formation in the western United States. This geological formation has preserved through layers of marine and alluvial sediments the history of an era dominated by colossal sauropod dinosaurs: Apatosaurus, Barosaurus, Brachiosaurus, Brontosaurus and Camarasaurus. The Diplodocus fossils abound in the middle and upper strata of the Morrison Formation, which correspond to the age of the Upper Kimmeridgian between 154 and 152 million years ago. Most of the bones of this dinosaur are common with the exception of the skull that is found very rarely and generally accompany the entire skeleton. The remains are scattered in several states of the rocky mountains of the American Midwest: Colorado, Utah, Montana and Wyoming.

Andrew Carnegie, Baron of Diplodocus

Dippy the Diplodocus
Andrew Carnegie and Dippy the Diplodocus

Andrew Carnegie was a business magnate and philanthropist who had a passion for dinosaurs and especially for Diplodocus. Thus, in the late nineteenth century and early twentieth, he financed a large number of expeditions to discover fossils of this sauropod. Thanks to numerous generous gifts of complete Diplodocus skeletons that he has made, the public can now contemplate this magnificent creature in many museums: the London Museum of Natural History as well as the Carnegie Museum of Natural History that he himself founded in the city of Pittsburgh to name a few.

Classification

Diplodocus belongs to the diplodocids family; extremely massive dinosaurs but thinner than their similar titanosaurs and brachiosaurs counterparts.

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