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The purpose of this project is to study the burrowing behavior and biogenic structures produced by extant terrestrial animals for the interpretation of continental ichnofossils. The major goals of this project are to identify burrow morphologies characteristic of specific taxa or body plans and to investigate the variation of burrow morphology due to changes in soil composition, consistency, moisture, and temperature. The results of this project will be invaluable to the identification and interpretation of subaerial exposure surfaces based on ichnofossils.

During the past year I have undertaken experimental research of the burrowing behaviors of nine different terrestrial arthropod taxa including three species of millipedes (Archispirostreptus gigas, Orthoporus ornatus, Narceus gordanus), two species of scorpions (Pandinus imperator, Hardrurus arizonensis), two species of whipscorpions (Phrynus marginemaculata, Mastigoproctus giganteus), one centipede species (Scolopendra alterans), and one trapdoor spider species (Myrmekiaphila coreyi). With these species I have completed several series of experiments involving the alteration of substrate composition and soil moisture in 30, 56, and 75 gallon aquariums. These experiments have yielded many excellent burrow casts for each group of animals which have been measured and described and are currently being compared using nonparametric statistics. Experiments involving alteration of surface temperature and its effect on burrowing behavior will be completed in the next two months after the installation of an environmental chamber in my laboratory.   

The research so far has yielded new information on the way in which terrestrial arthropods construct burrows, how they behave below the soil surface, and how they alter the soil environment. For example, predatory terrestrial arthropods such as scorpions and whip scorpions, which have been generally regarded as minimally involved in soil processes, have been found to be capable of moving large volumes of soil and sediment. In the process, these animals improve the quality of the soil and alter the surface environment. Each species currently under study is represented by a unique array of burrowing methods and morphologies, some of which vary with changes in the soil environment. The way in which the animals burrow has been found to have the greatest effect on their ability to handle changes in environmental conditions. Animals that are substrate excavators (physically move sediment particles from the subsurface to the surface) are able to burrow into the widest range of substrates (composition, consistency and moisture). These animals tend to inhabit regions with seasonal climates. Those animals that burrow by intrusion or compression (create openings by compacting sediment below the surface) tend to have more tightly constrained environmental requirements. These animals typically inhabit warm, wet environments.

The identification of the unique burrow morphologies produced by these terrestrial arthropods will be invaluable in identifying subaerial exposure surfaces where pedogenic overprinting is poorly developed or poorly preserved. In the Pennsylvanian strata of southeastern Ohio, the identification of continental ichnofossils has been very useful in locating sequence boundaries and lowstand deposits. The continental origin of many of these ichnofossils was difficult to determine until this experimental research was undertaken.

This grant has supported two undergraduate students as laboratory assistants. Their duties have included daily animal care and laboratory maintenance as well as assisting in experimental setup, data collection, and the description of burrow casts. As part of this job I have been instructing these students on the field of ichnology and assigned readings to aid in their understanding of the project. The students have also been directly involved in the setup of the experiments and in the collection of data during the experiments. Both students are coauthors on a talk to be given at the 2010 Geological Society of America Annual Meeting and a research paper currently in preparation.

I have presented results of this research at two conferences in 2009, the 9th North American Paleontological Convention and the Geological Society of America Annual Meeting, and one conference in 2010, the Third International Palaeontological Congress. An additional presentation will be given at the 2010 Geological Society of America Annual Meeting. I currently have two manuscripts in preparation that will be ready for submission by the end of 2010. In addition, I have presented my research in invited colloquia at the University of Akron, Ohio and the Nanjing Institute of Geology and Paleontology, China. I have also been interviewed by the Ohio University Alumni magazine, Perspectives, and was featured in an article discussing my research in the Autumn/Winter 2009 issue.