Apatosaurus was one of the more common sauropods in the Morrison, along with Diplodocus and Camarasaurus. It is a dinosaur which lived approximately 150 million years ago during the Jurassic Period. The name Apatosaurus means “deceptive lizard”. It was given this name by Othniel Charles Marsh because its bones resembled the bones of other dinosaurs, particularly Mosasaurs. Apatosaurus was gigantic. It was about 90 feet long, about 15 feet tall at the hips and weighed approximately 38 tons. Apatosaurus could have reared up on its front legs and brought them down with crushing force on an attacker or used its tail as a whip in defense. This animal was a herbivore, which means that its diet consisted of main leaves and other plant material. It had chisel-like teeth that could quickly remove the leaves from branches, but it didn’t chew up the plant material with its teeth. The scientists now believe that these animals swallowed stones to help them grind up plant material in their stomachs. Rocks used in this way are called gizzard stones or gastroliths. Most people refer to the Apatosaurus as the Brontosaurus. That’s because of a naming error that occurred early on in the discovery of these dinosaurs. The first one was named Apatosaurus, but one that was found later was called Brontosaurus. The public latched on to the name Brontosaurus, however, and it stuck. Unfortunately, according to the scientific convention, the oldest name is the proper name to use.