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 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