WHAT MADE THAT? IMPROVING THE INTERPRETATION OF CONTINENTAL TRACE FOSSILS THROUGH EXPERIMENTAL NEOICHNOLOGY

Our knowledge of the burrows produced by modern continental animals is limited. This makes the interpretation of continental ichnofossils difficult and inhibits our understanding of ancient soil ecosystems despite the presence of plant and animal trace fossils in even Early Paleozoic paleosols. Actualistic studies of living animals in the field and laboratory provide the data that make trace fossils invaluable to paleoecological and paleoenvironmental reconstructions. These studies allow for the interpretation of tracemakers, associated behaviors, and the environmental factors that influenced burrow production. The goal of this project is to determine how well burrows produced by known continental tracemakers engaged in known behaviors under controlled environmental conditions can be differentiated on the basis of morphology alone. This project involved the analysis of scorpion, whip scorpion, millipede, centipede, salamander, and skink burrows produced in a laboratory setting. The burrows include a diverse assemblage of shafts, ramps, U-, J-, W-, Y-shaped and helical burrows, mazeworks, and boxworks. Qualitative burrow descriptions include basic architecture, shape, orientation, internal structure, and surficial features. Quantitative descriptions include depth, slope, total length, tunnel width, height, and circumference, complexity, and tortuosity. On average, each animal species produced three distinct burrow morphologies, although there was overlap in basic burrow architectures between taxonomic groups. The quantitative aspects of the burrow morphologies were compared using nonparametric similarity and distance indices as well as cluster analyses to determine if the burrow casts could be effectively differentiated based upon their tracemakers, behaviors, and environmental conditions. By using multiple properties of burrow morphology to compare the burrows statistically, the burrows could be separated by different behaviors and tracemakers. Levels of similarity were highest amongst animals with similar morphologies, burrowing techniques, and behavioral patterns. Differences due to environmental conditions were minimal. The results from these experiments provide an assessment of our ability to reconstruct ancient soil ecosystems based on trace fossil morphology.