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
Dinosaur State Park and Arboretum a new state office building. The site opened as Dinosaur State Park in 1968, the same year its dinosaur trackway was memorialized as a Registered National Landmark. The park's geodesic dome (see picture at right) encloses some 500 tracks while another 1,500 remain buried for preservation. The tracks are from the early Jurassic period and were made over 200 million years ago on what must have been a sandy shore of a lake, by a carnivorous dinosaur similar to "Dilophosaurus". The tracks bear the name "Eubrontes", the term for fossilized footprints invented by geologist Edward Hitchcock. The tracks range from