Apatosaurus of gigantic sauropod dinosaurs. The family includes some of the longest creatures ever to walk the earth, including "Diplodocus", "Supersaurus", and "Barosaurus". "Apatosaurus" is sometimes classified in the subfamily Apatosaurinae, which may also include "Suuwassea", "Supersaurus", and "Brontosaurus". Othniel Charles Marsh described "Apatosaurus" as allied to "Atlantosaurus" within the now-defunct group Atlantosauridae. In 1878 Marsh raised his family to the rank of suborder, including "Apatosaurus", "Atlantosaurus", "Morosaurus" (="Camarasaurus") and "Diplodocus". He classified this group within Sauropoda, a group he erected in the same study. In 1903 Elmer S. Riggs said the name Sauropoda would be a junior synonym of earlier
Apatosaurus on the anterior end. The pelvic girdle includes the robust ilia, and the fused (co-ossified) pubes and ischia. The femora of "Apatosaurus" are very stout and represent some of the most robust femora of any member of Sauropoda. The tibia and fibula bones are different from the slender bones of "Diplodocus" but are nearly indistinguishable from those of "Camarasaurus". The fibula is longer and slenderer than the tibia. The foot of "Apatosaurus" has three claws on the innermost digits; the digit formula is 3-4-5-3-2. The first metatarsal is the stoutest, a feature shared among diplodocids. The name "Apatosaurus ajax" was