Abstract
Seismosaurus halli, gen. et sp. nov. (Sauropoda, Diplodocidae) is a new large sauropod from the Brushy Basin Member of the Morrison Formation (Upper Jurassic/Lower Cretaceous) of central New Mexico. The holotype is a partially articulated skeleton consisting to date of approximately 20 caudal vertebrae, five sacral vertebrae, eight dorsal vertebrae, partial pelvis, five chevrons, and ribs. Distinguishing features include the structure of the caudal vertebrae, pelvis, and chevrons. The extraordinary dimensions of these bones indicate an axial length of 39–52 meters.