. Bulletin. Natural history. 80 PEABODY MUSEUM BULLETIN 35 Sternal bone. An incomplete, thin plate of bone, suboval in shape and measuring 39 by 27 cm, was found directly beneath the left ischium. It has been catalogued with the latter as YPM 5449 and referred to the previously described vertebrae. The identity of this bone is questionable, but it clearly is not part of either ischium or part of the pubis or ilium. The margins are preserved on two sides and one end, and the shape of this portion corresponds very closely to the anterior half of a right sternal bone, par- ticularly that referred
. Bulletin. Natural history. 80 PEABODY MUSEUM BULLETIN 35 Sternal bone. An incomplete, thin plate of bone, suboval in shape and measuring 39 by 27 cm, was found directly beneath the left ischium. It has been catalogued with the latter as YPM 5449 and referred to the previously described vertebrae. The identity of this bone is questionable, but it clearly is not part of either ischium or part of the pubis or ilium. The margins are preserved on two sides and one end, and the shape of this portion corresponds very closely to the anterior half of a right sternal bone, par- ticularly that referred to Apatosaurus excelsus (YPM 1980) by Ostrom and Mcintosh (1966). It is less robust than that element and approximately four fifths as large. This bone is very different from the sternal bones of Alamosaurus which have a strongly concave external margin. Ulna. A left ulna was recovered close to the right ischium and is presumed to be- long to the same individual. Although somewhat distorted by crushing, it is almost complete and provides a reasonably close approximation to the original form. It is straight and of rather slender proportions, measuring 60 cm in length, cm in greatest proximal width, 12 cm in distal width and cm in minimum girth of the shaft (Plate 14: D). The ulna tapers gradually away from the proximal end, with the least diameter just below midlength. The proximal flanges are well developed and broadly rounded, the internal flange being the largest. These are separated by a rather deep radial concavity. The relatively slender proportions of the ulna are similar to those in Diplodocus or Brachiosaurus, although the ulna of the latter is much longer relative to ischium length than in the present specimen. This slenderness is in sharp contrast to the short massive proportions in Camarasaurus and Apatosaurus. discussion: Definitive evidence is not available for confident assignment of these remains. The dorsal vertebrae are consistent with both titanosau
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