are reminiscent of more derived sauropods. They are similar in morphology to Euhelopus, being concave on one side as well as having crowns with fairly great expansions. They are also similar to Camarasaurus, although the latter genus has less of a concavity and expansion. The teeth also possess marginal denticles on the crown. Based on histological studies, an individual of Patagosaurus would have replaced a tooth every 58 days, similar to 62 days for Camarasaurus, and 34 days for Diplodocus. Postcranial skeleton Most of the postcranial skeleton is known in Patagosaurus. The cervical, caudal and dorsal vertebrae are generally similar to Camarasaurus, although the sacrum possesses many distinct features. The sacrum is well preserved, showing that Patagosaurus possessed five sacral vertebrae. All the vertebrae but the fifth are fused together. All the neural spines are tall, and the centra are occasionally transversely narrow. The neural canal of the vertebrae is unique among sauropods, however. Starting from the very end of the first vertebra, and extending to almost the end of the third there is an enlargement of the canal, forming a well-defined cavity. Even though the sacrum itself is distinguishing, its sacral ribs resemble Camarasaurus. The sacral vertebrae have a total length of , with the total sacral length being . The pelvic girdle is well preserved and well studied. In the holotype, the pelvic girdle is almost complete, only lacking the proximal ends of each ischium. The ilia of the holotype are well known, and show many distinct features. The pubic peduncle, where the ilium articulates with the pubis, is long and straight and has an expansion on the end, as in many sauropods. The upper edge of the iliac blade is curved and thick, with rugosities (rough spots) for cartilage attachment. The pubic elements are large and robust in adults, more so than in juveniles. They are flat when viewed from in front, and convex when seen from behind. Lapparentosaurus resembles Patagosaurus when comparing their pubes. The ischia are much more gracile than the pubes, and only have a small distal expansion. While the ilia resemble Barapasaurus, and the pubes resemble Lapparentosaurus, the ischia are most similar to Diplodocus and Apatosaurus. The hindlimbs of Patagosaurus are based on scant material, some femora, a tibia and a few nondescript pedal bones. Two femora come from an adult, with a single additional bone known from the juvenile. The adult femora