Paleoecological research projects in the Columbia Basin have focused on mammalian species identification, with little regard for identifications of the comparatively few recovered reptile or amphibian (“herptile”) elements. Yet herptiles play extremely important roles in ecosystems and can be a key indicator of ecosystem health. Here we asked whether a combination of archaeological and paleoecological excavation methodologies would increase palaeo-herptile element recovery compared to previously published methodologies. Current research at the Coyote Canyon Mammoth Site (CCMS), Benton County, Washington, implemented such an excavation methodology with the goal of recovering previously under-reported microfauna. These methodologies include the establishment of a grid system of thirteen excavation units (XUs) measuring 2m x 2m, with each subsequently sampled in vertical increments of 10 cm levels, with several currently excavated to a vertical distance of 300 cm (or 30 levels). All excavated sediments are recovered and processed through a wet screen with 1 mm x 1 mm mesh allowing for the capture of sediment and organics that are then air-dried, bagged and labeled for future processing. Controlled excavation and wet screening remove enough extraneous matrix sediment while retaining critical microfaunal elements for a more accurate spatial and temporal representation of past community structure.
Results/Conclusions
Preliminary analysis of palaeofaunal remains from CCMS XU1, level 15, yielded a tiny Phrynosomatidae (horned lizard) maxilla of the genus Phrynosoma. This relatively complete specimen has a total length of 5.5 mm, height of 2.167 mm, and width of 1.0 mm. As such, this maxilla offers the first documentation of the paleontological presence of Phrynosoma at our site, and at any paleontological site within this region. Based on current knowledge (01 May 2020), level 15 dates to approximately 13,000 ± 500 years ago. The recovery of this element would have been unlikely with past excavation methods involving random surface prospecting, bucket/bag sampling, and dry screening with greater than 1 mm steel mesh. Continuing documentation of such finds at CCMS will provide crucial context for the herptile fauna of this region (particularly their community structure and taxonomic abundances), which have almost certainly been undersampled using prior methodologies that are biased against the recovery of smaller bone elements. Where possible, future paleoecological research could profit from adopting this more sensitive herptile micro-methodology to allow for more precision in reconstructive interpretation.