323-7 Digging into Diversity Dynamics: Vertebrate Faunas from Holocene Painted Rock Shelters Near the Pecos River in Arid Western Texas

Abstract:

Excavation of two small painted rock shelters on the western part of the Edwards Plateau by SMU produced archeological and faunal remains that have been largely unstudied. Artifacts (arrowheads and dart points) and the Pecos River style paintings in the Sotol (41CX9) and Meadows (41CX3) sites point to a range of dates for the shelter deposits extending across the middle to late Holocene (500-6,000 years BP for Sotol and 500 years BP for Meadows). That time interval in the Pecos River area experienced variation in aridity interrupted by more mesic conditions. We investigated these vertebrate fossils and the paleoecology of the sites across this background of changing climate, as well as compared these sites to each other and other sites in the Pecos River area to better understand potential changes to arid land faunal composition and dynamics. Our study and identification of >2,000 bone fragments from the sites reveal a diverse fauna comprised of ~30 species of fish, amphibians, snakes, turtles, birds, and mammals ranging from a few grams to 1,000 kg. The fauna is dominated by mammals including rabbits (Lepus, Sylvilagus) and rodents (Cratogeomys, Neotoma, Sigmodon, Peromyscus). Other abundant groups are carnivores (Vulpes, Urocyon, Canis) and ungulates (Odocoileus, Bison, Antilocapra). The shelter faunal assemblages are representative of habitats in the area, including the river valleys (cotton rat, pocket gopher, quail), river/streams (muskrat, soft shell turtle, catfish), rock shelters (woodrat, coyote, raptorial bird), and dry mesas (jackrabbit, roadrunner). Among that diversity, the only species not present in the area today is bison, pointing to a broad stability of the faunal diversity over thousands of years. The rock shelter faunas appear isotaphonomic (and thus comparable) with a shared combination of human impacts (cut marks, burned bones, fractured bones), small skeletal fragment sizes, and natural accumulation via carnivore (mammal, reptile, and avian) action, along with that of woodrats. Faunal comparisons of Sotol, Meadows, and other sites demonstrate similar faunal lists, and little stratigraphic variation in fish (Sotol) also points to no obvious impact of Holocene climate change. However, the rabbit relative abundance decreased in the top portion of the Sotol sequence (coincident with Meadows), and in-depth statistical treatments may uncover more subtle climate related variation in these and other area faunal assemblages.  

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