Allosaurus fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphans, several species of pterosaur, numerous dinosaur species, and early mammals such as docodonts, multituberculates, symmetrodonts, and triconodonts. Dinosaurs known from the Morrison include the theropods "Ceratosaurus", "Ornitholestes", "Tanycolagreus", and "Torvosaurus", the sauropods "Haplocanthosaurus", "Camarasaurus", "Cathetosaurus", "Brachiosaurus", "Suuwassea", "Apatosaurus", "Brontosaurus", "Barosaurus", "Diplodocus", "Supersaurus", and "Amphicoelias", and the ornithischians "Camptosaurus", "Dryosaurus", and "Stegosaurus". "Allosaurus" is commonly found at the same sites as "Apatosaurus", "Camarasaurus", "Diplodocus", and "Stegosaurus". The Late Jurassic formations of Portugal where "Allosaurus" is present are interpreted as having been similar to the Morrison but with a stronger marine influence.
Apatosaurus names; he grouped "Apatosaurus" within Opisthocoelia. Sauropoda is still used as the group name. In 2011, John Whitlock published a study that placed "Apatosaurus" a more basal diplodocid, sometimes less basal than "Supersaurus". Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015). It was believed throughout the 19th and early 20th centuries that sauropods like "Apatosaurus" were too massive to support their own weight on dry land. It was theorized that they lived partly submerged in water, perhaps in swamps. More recent findings do not support this; sauropods are now thought to have been fully terrestrial animals. A study