HAIR TRACES IN CARNIVOROUS COPROLITES

Preliminary analysis of carnivorous coprolites from the White River Group (early Oligocene, Orellan Mammal Age) for hair trace fossils suggests a high likelihood for preservation in any carnivorous coprolite. Hair (keratin protein) is indigestible, and predators that eat mammals or have fur of their own will have hair in their feces. White River samples have typical coprolite preservation, and since carnivorous coprolites can be locally abundant fossils (due to bone mineral content), they have great potential in illuminating when hair evolved and possibly among which synapsid clades. In addition, hair morphology is sometimes ecologically and taxonomically informative. Sectioning with a knife or chisel, sanding, HCl acid etching, sonic cleaning, and gold coating were determined to be the best steps in preparing inner coprolite surfaces. Because these coprolites are cemented with calcium carbonate, acid etching is damaging as well as revealing, so some surfaces were prepared without etching. Each of four coprolites were sectioned into multiple samples and initially scanned under low magnification. Though each coprolite contained hair traces, traces occur at a low density, and calcite hair casts have a low contrast with surrounding matrix, so searching is time intensive. One high-density patch of traces (mainly molds) was observed in each coprolite, and individual casts or molds were found sporadically throughout the matrix. The most prolific coprolite contained traces next to rodent foot bones. In modern hair shaft diameters typically range from 10-60 microns, and fossil traces were 20-70 microns wide. Exposed hair shaft casts ranged in length from 75-150 microns. From repeated sanding of one hair trace patch, some hair molds may be at least several millimeters long. In these silty coprolites, hair cuticle preservation is rare—about one hundred traces revealed only one cuticle pattern. This hair cast was 45 microns wide and 120 microns long, exhibiting only three scales in a simple coronal pattern. Except for bone and one pollen grain, no other fossils, such as fungal hyphae or parasites, were observed.