TRACKING THE ELUSIVE SAUROPODS AND PTEROSAURS AT SEMINOE RESERVIOR IN SOUTH-CENTRAL WYOMING

The Morrison Formation of Wyoming has long been famous for containing dinosaur fossils, while the Sundance Formation is traditionally known for its marine sediments and associated fauna. The recent discovery of sauropod dinosaur tracks in the Morrison Formation and pterosaur tracks in the Sundance Formation near Seminoe Reservoir in Carbon County, Wyoming is important to the understanding of the terrestrial vertebrate faunas at these times. Documentation at this site includes detailed ground measurements, mapping, photography, mylar sketches and photogrammetry.

Preliminary documentation of the sauropod imprints reveals approximately 30 well-exposed tracks in 20-meters of a tan, very fine-grained sandstone layer of the lower Morrison Formation. Tracks vary in size, with widths ranging from 6 to 33 cm, lengths ranging from 15 to 52 cm, and depths ranging from 2 to 12.5 cm. Many of the sauropod tracks display compacted layers, overprinting and high impact rims. The variations in track size and depth, suggest the preservation of the footprints of several animals, as they walked in a water-saturated sedimentary environment.

Over 70 pterosaur tracks are preserved as natural molds and casts in a fine-grained, ripple-marked, quartz sandstone of the upper Sundance Formation. Preserved in the sediments of an ancient tidal flat, the pes impressions typically display four digits, while tracks of the manus show three digits. Pes lengths vary from 6 to 10.2 cm, while pes widths range from 2.1 to 2.8 cm. Twelve trackways have been located displaying manus prints lateral to the pes prints. Trackways, from animals of various sizes, vary from two to six sets of pes and manus traces. The high number of pterosaur tracks in the area at Seminoe Reservoir is similar to other tracksites of pterosaurs from the late Jurassic Period. Sufficient evidence exists to match these traces to other identified Pteraichnus tracks located in the Sundance Formation of Wyoming, Utah, Arizona, Colorado and Oklahoma. Intensive documentation of these tracks will provide valuable information for understanding the terrestrial-quadrupedal movements of these unique volant reptiles.