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Diplodocus was one of the largest sauropod plant-eaters during the Jurassic period. It lived between 155 and 145 million years ago. Diplodocus grew to be about 90 feet long. It had a long, 26-foot neck and a flexible 45-foot tail. That’s about as large as an airplane. It was among the longest land animals that ever walked on the planet. It was also heavy, although not as heavy as a Brachiosaurus. It weighed about 15 tons. Its nostrils were at the top of its head. Some paleontologists believed that this allowed Diplodocus to spend more of its time underwater. Now we believe this dinosaur was more of a land creature. Diplodocus was not a very intelligent dinosaur. Its head was less than two feet long. The space in its skull for a brain was very small. Some paleontologists think that Diplodocus had a second brain in its backbone near the hips. This might have helped send messages from its brain to its back legs and tail. Diplodocus moved slowly. Like most dinosaurs, its front legs were shorter than its back legs, so its neck stretched out straight from its body. This meant it could sweep the ground of low-lying plants as well as reach the tops of trees. It had five elephant-like toes on each big, round foot. Each foot also had a sharp thumb claw. This was probably used to defend against predators.

From fossils we have learned that Diplodocus had a row of small spikes running down its back. This was useful protective armor for these large creatures. The name “Diplodocus” means "double-beamed”. This unusual name comes from the bones on the bottom of its tail. The vertebrae along its tail had extra T-shaped bones pointing downwards. These strange bones let Diplodocus hold its long tail straight out behind it. With this extra support, Diplodocus could move its tail around like a whip. It was useful for balance and also for protection against hunters. Diplodocus was an herbivore, meaning that it only ate plants. It had small, blunt teeth, but only in the front of its mouth. This was useful for stripping leaves off trees. But it also meant that it probably couldn’t chew its food. Its main food was the leaves from conifers, which are trees that grew in many places during the Jurassic. It may also have eaten the leaves from gingko trees, ferns, cycads, mosses, and horsetails. Paleontologists believe it had to eat between 300 and 400 pounds of leaves a day! Like many large sauropod dinosaurs, it may have swallowed small stones called gastroliths with its meals. Gastroliths would stay in its gizzard and grind tough plant leaves into a mushy paste. Then the food would move on to the stomach for digestion.

Diplodocus may have moved from place to place in large groups or herds. When a group had eaten all the food in one area, they would migrate - or travel - to another place. When they were on the move, the larger, stronger adults walked along the outside. The young stayed in the center of the herd. This was done to protect them against predators. Diplodocus hatched from eggs, like all other dinosaurs. These eggs were not laid in nests but in straight lines along the ground. This may have meant that these dinosaurs laid their eggs as they walked. Once they hatched, the babies had to fend for themselves. If they lived to become adults, they could live to be 100 years old. Diplodocus fossils have been found in the Rocky Mountains in North America: in Colorado, Montana, Utah, and Wyoming.

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