RESULTS OF THE SUMMER 2020 PALEONTOLOGICAL FIELD SURVEY CONDUCTED IN BADLANDS NATIONAL PARK, SOUTH DAKOTA

Badlands National Park, South Dakota, protects significant Mesozoic to Cenozoic (75-28Ma) marine, fluvial, and aeolian deposits with associated vertebrate and invertebrate fossils. During 2020, a paleontological field survey was conducted on deposits of the basal Scenic Member, Brule Formation (Early Oligocene, ~33.7Ma). The survey entailed prospecting and identifying micro- and macro- fossil assemblages in a given area to establish localities based on taxonomic diversity and specimen density. Five new localities were documented from the lowermost unit of the Scenic Member, which unconformably lies upon the Chadron Formation. The interbedded calcareous mudstones, siltstones, and sandstones preserved at least 45 distinguishable taxa within fluvial and lacustrine deposits. These taxa include freshwater gastropods, fish, an amphibian, testudines, carnivores, rodents, lagomorphs, an insectivore, perissodactyls, artiodactyls, and ichnofossils. These taxa support current interpretations of the Scenic Member as a forested riparian environment with associated open, grassy woodland and scrublands, with each locality representing unique micro-environments as evidenced by the freshwater invertebrates and fish. The most noteworthy finds are an ursid Drassonax harpagops, which is the first confirmed occurrence within park boundaries and represents a temporal and geographical range extension for the genus, and the spadefoot toad Scaphiopus, which is a temporal range extension. The results of this survey project, and the discovery of a new taxa never seen in the park, highlights the importance of exploring unsurveyed areas. The documentation of several poaching incidents within the surveyed area also indicates the value of ongoing site monitoring. These are crucial tools for advancing paleontological knowledge, protecting the information contained in the natural resource, and implementing NPS mission-critical resource management practices.