Apatosaurus << uh `pat` oh SAWR uhs or `ap` uh toh SAWR uhs >> was a gigantic dinosaur with a long neck. It belonged to the group of plant-eating dinosaurs called sauropods. Apatosaurus lived about 150 million years ago in what is now the western United States.
Apatosaurus grew to about 75 feet (23 meters) long and 15 feet (4.5 meters) tall at the hip. It weighed about 20 to 30 tons (18 to 27 metric tons). Some individuals may have grown to be much larger and heavier.
Apatosaurus had a small, narrow head at the end of its long, heavily muscled neck. The neck made up more than quarter of the animal’s length. It was far thicker and more solidly built than the necks of other sauropods. Apatosaurus may have used the neck to club predators (hunting animals) or rivals. Apatosaurus had a relatively short body, with its back sloping gently down from hips to shoulders. Its long tail was thick at the base but narrowed to a thin, whiplike tip. A pair of massive hind limbs bore most of the animal’s weight. The hind limbs had padded feet with large claws. The forelimbs of Apatosaurus were relatively short, and each forefoot had only one small claw.
Since its discovery, Apatosaurus has been linked to another sauropod, Brontosaurus. The American paleontologist (scientist who studies prehistoric life) Othniel C. Marsh first described an incomplete fossil skeleton of Apatosaurus in 1877. Two years later, he discovered another, more complete skeleton and named it Brontosaurus. During the 1900’s, however, scientists concluded that Apatosaurus and Brontosaurus were the same kind of dinosaur. The Apatosaurus name was kept because it came first, but the name Brontosaurus had become famous and remained in popular use. In 2015, paleontologists again studied the fossil skeletons and concluded that Brontosaurus and Apatosaurus may be two distinct kinds of dinosaurs after all.
