Brachiosaurus

Brachiosaurus was a huge plant-eating dinosaur that lived in what is now North America about 154 million years ago. Its name means "arm lizard," because its front legs were longer than its back legs. That gave its body a tilt like a giraffe. Brachiosaurus belonged to a group of long-necked dinosaurs called sauropods.

It was one of the tallest animals that ever walked on Earth. With its neck stretched up, Brachiosaurus could reach about 40 feet into the air. That is as tall as a four-story building. From nose to tail, it was around 70 feet long. Scientists think it weighed between 30 and 60 tons. Even the smaller guess is about the weight of ten elephants.

Brachiosaurus ate only plants. It used its neck like a crane to reach leaves high in the tops of trees. Other plant-eating dinosaurs fed closer to the ground, so they did not have to fight over the same food. Its teeth were shaped like chisels, good for stripping leaves off branches. It did not chew much. Instead, it swallowed leaves whole and let its enormous stomach break them down for days.

An animal that big needed a lot of food. Scientists guess Brachiosaurus had to eat hundreds of pounds of plants every day. Its heart was also huge. Some scientists think it may have weighed 400 pounds, about as much as a large motorcycle. The heart had to be that strong to push blood all the way up that long neck to the brain.

Paleontologists still argue about how Brachiosaurus lived. For a long time, people thought it spent most of its time in water, using lakes to hold up its heavy body. Newer research shows that its legs were strong enough to carry it on dry land, and its lungs would not have worked well underwater. Most scientists now picture Brachiosaurus walking through open forests, not wading in swamps.

The first Brachiosaurus bones were found in 1900 in Colorado by a fossil hunter named Elmer Riggs. A famous skeleton now stands in a museum in Berlin, Germany, and another is mounted at Chicago's O'Hare Airport. Movie fans may also remember Brachiosaurus as the first dinosaur the characters see in the film Jurassic Park.

Brachiosaurus died out more than 140 million years ago, long before the asteroid that killed the last dinosaurs. We only know it existed because of the bones it left buried in the rock.