THE POISON CREEK DINOSAUR FAUNA FROM THE UPPER JURASSIC MORRISON FORMATION, JOHNSON COUNTY, WYOMING

From 1976 until 1991, crews from the Science Museum of Minnesota (SMM) excavated over 1000 dinosaur skeletal elements from a quarry in the Morrison Formation located in Johnson Co., WY. Detailed field notes and a carefully surveyed quarry maps were maintained during the excavations. The skeletal elements were prepared by SMM staff and volunteers during the intervening years. Skeletal displays of Diplodocus, containing approximately 70% original material from the quarry, and Camptosaurus, with approximately 20% original material, are on display. Unfortunately, little else has been done with the collection.

A taphonomic study of the Poison Creek dinosaur fauna has been initiated in order to increase our understanding of the Late Jurassic Morrison ecosystem. As a starting point, it is necessary to determine the minimum number of individuals and species present. A right humerus and cervical vertebrae diagnostic of the ornithopod Camptosaurus are part of the fauna. Additionally, a theropod pubis and teeth were recovered and appear to belong to Allosaurus. The occurrence of 10 right sauropod humeri has been identified. Therefore, a minimum of 12 individuals are known to be present in the fauna of the study site.

Identification of the sauropod species in the fauna is underway. The presence of nearly complete skulls of Diplodocus and Camarasaurus establishes the presence of these two sauropods in the fauna. One of the humeri is decidedly larger and more robust and has been tentatively described as belonging to the genus Haplocanthosaurus. Cervical vertebrae are the most diagnostic elements for sauropods and approximately 18 complete elements are present. Analysis of these elements is being conducted.