Apatosaurus which Marsh had described "Brontosaurus". Most of the skeleton was found, and after comparison with both "Brontosaurus" and "Apatosaurus ajax", Riggs realized that the holotype of "A.ajax" was immature, and thus the features distinguishing the genera were not valid. Since "Apatosaurus" was the earlier name, "Brontosaurus" should be considered a junior synonym of "Apatosaurus". Because of this, Riggs recombined "Brontosaurus excelsus" as "Apatosaurus excelsus". Based on comparisons with other species proposed to belong to "Apatosaurus", Riggs also determined that the Field Columbian Museum specimen was likely most similar to "A.excelsus". Despite Riggs' publication, Henry Fairfield Osborn, who was a strong
Apatosaurus have a close counterpart"Brachiosaurus" and "Lusotitan", "Camptosaurus" and "Draconyx", and "Apatosaurus" and "Dinheirosaurus". Other vertebrates that are known to have shared this paleo-environment include ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphans, and several species of pterosaur. Shells of bivalves and aquatic snails are also common. The flora of the period has been evidenced in fossils of green algae, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers. Vegetation varied from river-lining forests of tree ferns with fern understory (gallery forests), to fern savannas with occasional trees such as the "Araucaria"-like conifer "Brachyphyllum". Apatosaurus Apatosaurus (;