Imaging coprolite taphonomy and preservation

The impact of coprolite taphonomy on parasite remains and aDNA recovery has been recognized. In general, coprolites from sites protected by geologic features such as caves and rock shelters exhibit the best preservation. In contrast, coprolites from open sites can be badly affected by taphonomic processes as shown by analyses of parasite eggs. For eggs, the impact of mites and free-living nematodes has been quantified. Mites are associated with poor pinworm egg preservation. In other studies, percolation of water through sediments has a negative impact on egg recovery. We note that dietary remains can also decompose at open sites. Through scanning electron microscopy (SEM), we present examples of screened but chemically untreated microscopic remains. Panorama SEM images provide an excellent visual overview of the taphonomy of dietary remains. For this study, our focus is on Southwestern coprolites as a demonstration of diversity within a single region. Examples from caves and rock shelters were examined first to describe the taphonomic challenges for protected sites. Then, attention was turned to coprolites from open sites. In general, the challenges noted for parasite preservation are seen for other microfossils. However, the preservation of lignin, sporopollenin, calcium oxalate, and siliceous microfossils is generally better than cellulose structures. These observations are relevant to the selection process of samples for aDNA analysis and immunological study. This is especially relevant for the gut microbiome since decomposer fungi and bacteria molecular signals could be recovered in metagenomic analysis.