Neoichnology of Extant Terrestrial Arthropods and Amphibians: The Key to Interpreting Pennsylvanian Continental Ichnofossils of the Appalachian Basin

The interpretation of ichnofossils, including their tracemakers, the behaviors involved, and the environments that influenced their production requires the study of modern organisms. While there are numerous examples of these types of studies with marine organisms, few have involved terrestrial burrowing animals. Ichnofossils are abundant in paleosols of the Late Pennsylvanian Conemaugh Group of southeastern Ohio. Many of the ichnofossils present in these paleosols have unique morphologies and likely represent new tracemakers and behaviors. In order to interpret the Conemaugh Group ichnofossils, the burrowing behaviors and biogenic structures of extant terrestrial animals were studied in a laboratory setting.

This project involved the study of a single scorpion species, Pandinus imperator, a single tailless whipscorpion species, Phrynus marginemaculata, two millipede species, Orthoporus ornatus and Archispirostreptus gigas, and a single salamander, Ambystoma tigrinum. These taxa were selected for their morphological, taxonomic, and ecological similarity to animals present in the Pennsylvanian of North America. The animals were placed in large, sediment-filled aquaria for two week periods during which their behavior and resulting biogenic structures were observed. Biogenic structures produced in the aquaria included subsurface burrows and chambers, as well as surface tracks and trails. Open burrows were cast with plaster and surface features were preserved with resin. Detailed descriptions of the morphologies of subsurface structures included basic architecture, surficial features, complexity, and tortuosity. The biogenic structures produced in the laboratory were then compared to similar ichnofossils from the Conemaugh paleosols.

Biogenic structures produced in the laboratory have permitted the interpretation of the Conemaugh Group ichnofossils. The majority of the ichnofossils represent locomotion, feeding, and dwelling behaviors of soil arthropods. Larger burrows were likely temporary to permanent dwellings of tetrapods. The type and diversity ichnofossils also provide data for the interpretation of soil consistency, soil moisture and water-table level, nutrient concentration, and sedimentation rates.