ANALYSIS OF JIM'S HADROSAUR SITE: A DINOSAUR SITE IN THE MIDDLE CAMPANIAN (CRETACEOUS) WAHWEAP FORMATION OF GRAND STAIRCASE-ESCALANTE NATIONAL MONUMENT (GSENM), SOUTHERN UTAH

The Utah Geological Survey (UGS), in cooperation with the Bureau of Land Management (BLM), has been conducting a multi-year project to inventory the paleontological resources of the Wahweap Formation (middle Campanian) of GSENM. In 2004, several tiny scraps of bones were found on a small hill near the base of the “middle mudstone member.” Preliminary surface excavation showed that the site contained the associated remains of a juvenile hadrosaur. Excavation of the site in the spring of 2005 resulted in the collection of over 30 elements of the post-cranial skeleton. Elements recovered include large portions of the forelimb, hindlimb, and girdles, as well as cervical, dorsal, and caudal vertebrae. Unfortunately, no portions of the skull were recovered that might allow for more specific taxonomic identification of this animal. In addition to the juvenile hadrosaur remains, portions of the carapace and plastron of an unidentified turtle of possible eucryptodire affinities were found mixed together with the hadrosaur bones. A tooth of the extinct bowfin, Melvius, several freshwater crab claws, and poorly preserved unionid bivalves were also collected from the site. The fossils were contained in a muddy sandstone unit that also preserved abundant sections of compressed carbonized log fragments, commonly over a meter in length. Some log sections preserve evidence of burning and others, insect burrowing. Smaller compressional plant fragments include mainly Araucaria, with rare Sequoia and angiosperms. Bones and logs are current oriented. We hypothesize that the juvenile hadrosaur carcass and the turtle carapace were washed down a small stream and were caught against a logjam. Recent work in the Wahweap Formation of GSENM has resulted in a number of scientifically significant dinosaur discoveries with hadrosaur and ceratopsian dinosaurs being most common. This site represents one of the few localities in the Wahweap Formation that contain an associated dinosaur skeleton, but illustrates the potential for further discoveries in this formation.