Reptilia - Dinosauria - Diplodocidae

Alternative combinations: Atlantosaurus excelsus, Brontosaurus excelsus, Camarasaurus excelsus

Synonyms: Apatosaurus amplus Marsh 1881, Atlantosaurus amplus Marsh 1881, Brontosaurus amplus Marsh 1881, Elosaurus parvus Peterson and Gilmore 1902

Full reference: O. C. Marsh. 1879. Notice of new Jurassic reptiles. American Journal of Science and Arts 18:501-505

Belongs to Apatosaurus according to P. Upchurch et al. 2004

Sister taxa: Apatosaurus ajax, Apatosaurus louisae

Type specimens:

• Apatosaurus excelsus: YPM 1980, a partial skeleton. Its type locality is Quarry 10, Como Bluff (YPM), which is in a Kimmeridgian/Tithonian wet floodplain claystone in the Morrison Formation of Wyoming.
• Brontosaurus amplus: YPM 1981. Its type locality is Quarry 11, Como Bluff (YPM), which is in a Kimmeridgian/Tithonian wet floodplain mudstone in the Morrison Formation of Wyoming.
• Elosaurus parvus: CM 566, a set of postcrania. Its type locality is Carnegie Quarry E, Sheep Creek, which is in a Kimmeridgian/Tithonian lacustrine horizon in the Morrison Formation of Wyoming.

Average measurements (in mm): femur 1732.4 x 310.0, femur circumference 730.0, fibula length 1130.0, humerus length 1100.0, radius 755.0 x 127.0, tibia length 1080.0, tibia circumference 480.0, ulna length 740.0

Estimated body mass: 32.4 tons based on femur circumference and femur length