Wikijunior:Dinosaurs/Apatosaurus

The Apatosaurus, whose name means "deceptive lizard" in Greek, was one of the largest land animals ever. For many years, this dinosaur was sometimes called Brontosaurus.

What did they look like?
The Apatosaurus was one of the largest land creatures that have ever lived. They were 20–27 metres in length, 3–5 metres in height, and weighed an enormous 30–35 tons! This is over 6 times heavier than an elephant!

They walked on four legs with a big muscular body, but a much smaller head attached on a long neck. They held their tail up a little above the ground as they moved. The main purpose of this tail was to make sure that the dinosaur would not fall over due to its heavy long neck. It was also used for defence against predators. Their heads were long and narrow. Strangely, apatosaurus's nostrils were on the top of its head; this is believed to have been so that it could breathe with all but the top of its head underwater, to hide from predators.

What did they eat?
They were herbivores &mdash; that is, they ate plants. There are two theories about how they used their necks when eating. Until recently, most scientists thought they used their long necks to reach up into trees to get leaves and branches; but recently, some scientists have suggested they used their long necks instead to feed from the ground. They could not chew; most scientists think they swallowed stones called gastroliths to help grind the food in their stomach! Because there were no broad leafed trees, they ate pine needles and ferns. There also was no grass.

When did they live?
They lived in the late Jurassic Period, about 157–146 million years ago. The Jurassic period was warm and humid and had lots of vegetation.

Where did they live?
When they were first discovered, scientists believed that because of their large size they could not live on land. So they would have to walk in water with their heads sticking out. Now scientists think that this is not true – no bones were found in any ancient watery places. They most likely lived near river banks where they could find both water and trees. They could not live in the forests, because they were simply too big to walk around in a forest!

Their fossils have been found in Colorado, Oklahoma, Utah, and Wyoming, in the USA, North America.



How were they discovered?
Professor Othniel Marsh discovered parts of the first fossils of a young Apatosaurus in 1877. The first Apatosaurus skeletons were found without heads. Because of the confusion with the Brontosaurus, the head of Apatosaurus was not conclusively identified until 1972. By this time many examples of the correct head had been found. Apatosaurus means "deceptive lizard," because its fossils were so similar to those of other sauropods.

What do we need to learn?

 * We need to learn how flexible their neck really was, whether they could raise it up high or whether it could only be raised slightly.
 * Where and how they really lived, all we have now are just some educated guesses.
 * Whether they lived alone or travelled in herds like their close relatives the Diplodocus.
 * How they laid their eggs.