Apatosaurus was a sauropod dinosaur that lived in the Jurassic period of the Mesozoic.
Apatosaurus is considered by most to be the benchmark sauropod. About 75 feet long, and weighing in at over 25 tons, this creature was a standard Diplodocid, with a long neck, whiplike tail, massive bulk, thick legs, and a long, suspension bridge-like design. For defense, Apatosaurus had a long, whiplike tail and could whip at potential predators; even so it would be a major target for a large theropod. Apatosaurus is typically depicted being hunted by Allosaurus; however certainly it would also have been hunted by megalosaurids as well.
The Western U.S. 150 million years ago would have been a wet, hot, mostly plains habitat with sparse forested areas. Apatosaurus wouls have lived in the plains regions, as a low-foliage grazer.
Apatosaurus lived alongside other herbivores like his fellow sauropods, Brachiosaurus and Diplodocus, and other plant eaters like Dryosaurus and Stegosaurus. It was likely hunted by large, pack-hunting Allosaurids, like Allosaurus and Torvosaurus. Apatosaurus was probably a herd animal.