COMPARISON OF THE PALEOECOLOGY OF THE MIDDLE EOCENE (BR-1A) FAUNA OF NATRONA COUNTY, WYOMING, TO THAT OF THE ECOLOGY OF TODAY

During the summer of 2013, the Teen Science Scholars at the Denver Museum of Nature & Science collected fossils in the Wind River Formation of Natrona County, Wyoming. Their work included collecting, analyzing, and researching diversity between the Early Eocene and Holocene non-volant mammals from the same geographic area. The question that arose was to compare the paleoecology of ancient Wyoming with the present day sagebrush grassland ecology. The goal was to ultimately understand species diversity in the two climatic extremes of the last 100 million years: Peak Warming at 50 million years ago and cool temperatures of today. Based on the fossil record of primates having morphology suggesting an arboreal behavior, it can be inferred that a subtropical closed canopy forest existed in the Wind River Basin during the Bridgerian (Br1a) of the Middle Eocene. Previous studies of leaf margin analysis in the Wind River Basin support the conclusion that ancient Wyoming during Br-1a had a temperature that was 13º centigrade higher and had a larger mean annual precipitation level than the Holocene Epoch in Wyoming. Dominating the Eocene Epoch were Primates and Perissodactyla. whereas today the dominating order is Artiodactyla. A number of families of mammals have gone extinct since the Eocene including Brontotheriidae, Paleotheriidae, Pantolestidae. Hyopsodontidae, Phenacodontidae, Cimolestidae, Hyaenodontidae, Omomyidae and others. Today the fauna includes Bovidae, Antilocapridae, and most other living mammalian families that are unknown in the Eocene. There were 56 genera of non-volant mammals during Br-1a compared to 37 today. The Eocene Epoch in Natrona County was more diverse because of the potential amount of occupiable niches in subtropical forests versus the dry and arid climate of contemporary Wyoming and the desert grassland ecosystem. The data conveys the idea that contemporary Wyoming is ill-suited for a large biodiverse environment and that higher temperatures imply greater biodiversity.