Apatosaurus considered a junior synonym of "Apatosaurus"; its only species was reclassified as "A.excelsus" in 1903. A 2015 study concluded that "Brontosaurus" is a valid genus of sauropod distinct from "Apatosaurus", but not all paleontologists agree with this division. As it existed in North America during the late Jurassic, "Apatosaurus" would have lived alongside dinosaurs such as "Allosaurus", "Camarasaurus", "Diplodocus", and "Stegosaurus". "Apatosaurus" was a large, long-necked, quadrupedal animal with a long, whip-like tail. Its forelimbs were slightly shorter than its hindlimbs. Most size estimates are based on specimen CM3018, the type specimen of "A.louisae". In 1936 this was measured to
Wyoming Dinosaur Center on the property is from the "Something Interesting" or SI excavation site. This site presents the rare occurrence of both dinosaur trace fossils and body fossils including footprints of many Sauropods and "Allosaurus" as well as skeletal remains from "Camarasaurus, Diplodocus," and "Apatosaurus" - three of the sauropods most common in the area during the Late Jurassic. Most of the bones belong to a juvenile (30 foot long) "Camarasaurus" that was scavenged by many "Allosaurs". This is known based on the presence of both teeth and claw marks on many of the bones present as well as an abundance of