DESCRIPTION AND PRELIMINARY TAPHONOMIC IMPLICATIONS OF THE PARTIAL SKELETAL REMAINS OF A DIPLODOCID SAUROPOD FROM THE UPPER JURASSIC MORRISON FORMATION OF UTAH

The partial skeletal remains of a diplodocid sauropod, tentativley identified as Diplodocus sp., were excavated (with permission from the Bureau of Land Management, Utah) during May 2000 from a fine to medium grained, well indurated fluvial sandstone of the Upper Jurassic Brushy Basin Member of the Morrison Formation. The quarry is located on the western flank of the San Rafael Swell in Emery County, east of Moore, Utah. Stratigraphically, the skeletal remains are 124 meters (407 ft.) below the base of the Lower Cretaceous Buckhorn Conglomerate Member of the Cedar Mountain Formation. The bones removed from the quarry to date include a 1.52 meter (5.00 ft.) left scapulocoracoid, the lower portion of a limb, several phalanges (including an ungual claw), three fairly complete articulated proximal caudal vertebrae, two almost complete ischia, portions of two pubes, several dorsal ribs (one having fairly complete capitulum and tuberculum portions and being about 1.2 meters in length), a chevron, and several other fragments of bone. The tentative identification of the sauropod as Diplodocus sp. is primarily based on the morphology of the scapulocoracoid and the caudal vertebrae. The size of the scapulocoracoid suggests an approximate length of 21 meters (about 70 ft.) for the sauropod. Additional bones remain to be removed from the quarry and work will continue during 2001. All bones found to date appear to belong to a single individual. The bones are scattered somewhat randomly with respect to the anatomy of the sauropod, however, several of the longer bones appear to have a consistent alignment in a northerly-southerly direction and may have been influenced by current action during transport and deposition. However, the bones are not heavily abraded and were probably transported only short distances. We speculate that the animal died on the floodplain and during a flooding event the exposed bones were disarticulated and washed into the stream channel and transported for a short distance.