Revisiting the Paleoenvironment and Mammal Fauna of the late Uintan Swift Current Creek Locality, Saskatchewan

Abstract

The Swift Current Creek (SCC) locality was previously described as being similar to the “Rocky Mountains” fauna, an informal grouping of near-coeval assemblages in Utah and Wyoming, but otherwise having high faunal endemism (Storer 1984). Its paleoenvironment was described as a semi-arid, “tropical,” enclosed forest (Storer 1984). This interpretation of its environment contradicts the “Rocky Mountains” fauna comparison, as its Utah component (Myton Pocket- MP) is now interpreted to have been a savannah. This thesis sought to review SCC’s paleoenvironment and faunal endemism using a revised faunal list with palaeoecological methods not applied during previous studies of SCC. First, a rarefaction analysis was used to quantify the locality’s level of sampling, the likelihood of finding new mammal genera, and the diversity of specific taxonomic groups. A cenogram analysis was used to interpret SCC’s paleoenvironment based on body mass distribution (BMD) data. Similarity index calculations served to quantify SCC’s generic faunal similarity with near-coeval localities, including the Rocky Mountain’s MP and Badwater 6 (BW6; in Wyoming) localities. Faunal endemism was interpreted using a distance decay regression analysis, with Holocene localities serving as a baseline for comparative interpretation of differing patterns in faunal similarity. The rarefaction analysis results indicated that SCC is moderately sampled, and that continued sampling may result in the discovery of new mammal genera (especially rodents). The cenogram’s BMD is reflective of a humid, warm, enclosed forest. Some diversity signals from the rarefaction analysis support the interpretations of SCC’s environment, while others leave room for doubt. Descriptions of SCC being similar to the “Rocky Mountains” fauna were found to be inaccurate. The Swift Current Creek locality has high similarity value with BW6, but not with MP. The distance decay regression for SCC and its coeval localities did not express a significant decline in faunal similarity, and the rate of declining faunal similarity was much less drastic than in Holocene localities; demonstrating that SCC’s faunal endemism is not as high as past literature has indicated.