X-RAY TOMOGRAPHIC MICROSCOPY SHINES A LIGHT ON FOSSILIZED FECES FROM THE EOCENE PIPESTONE SPRINGS MAIN POCKET, MONTANA

The study of coprolites and their internal constituents has previously employed a predominantly destructive means preparation, resulting in the partial or complete loss of the specimen. There have been several recent studies, however, that have adopted a more modern approach of data collection and analysis, incorporating three-dimensional imaging techniques such as x-ray tomographic microscopy (µCT) and synchrotron microtomography. These non-destructive methods permit virtual extraction of qualitative information on the identity, structure, and orientation of coprolite inclusions, as well as important quantitative information such as morphometrics and the proportion of inclusions to matrix.

Herein, we apply µCT to study bone and other miscellaneous inclusions in two size classes of coprolites (small = 4–15mm; large = 16–29mm) previously attributed to Hesperocyon and Brachyrhynchocyon from the Pipestone Springs Main Pocket assemblage, Renova Formation, Montana. Segmentation of µCT data was used to document the degree of skeletal fragmentation, as well as the proportion of bone material to phosphatic matrix, which in sum provide novel insights into both the feeding behavior of the producers and the taphonomy of inclusions. Among the features identified in µCT were: 1) skeletal fragments, including those showing evidence of bone-crushing; 2) delicate molds of mammalian hair; 3) lithic fragments encrusted on the coprolite surface; and 4) several pores and cracks throughout the coprolites samples. In combination with volume renders of the virtually extracted material, we also adopt more traditional methods such as thin-section petrography and SEM-EDS analysis to characterize the taphonomic attributes of the samples. We emphasize that traditional methods are not obsolete, as they provide data that cannot be obtained using digital methods; however, µCT enabled specific targeting of areas of interest prior to destructive sampling. Together, newer methods of digital dissection in conjunction with traditional sectioning methods complement one another towards a more holistic view of coprolite features and insights into the broader paleoecology of their producers.