NEOICHNOLOGY OF THE WHIP SCORPION PHRYNUS MARGINEMACULATA: INTERPRETING THE ROLE OF PREDATORY ARTHROPODS IN EARLY SOIL ECOSYSTEMS

Soils are highly buffered environments and were, therefore, one of the earliest terrestrial environments to be colonized in the Paleozoic. Modern soils contain diverse ecosystems that include micro- and macrofauna with a number of different feeding strategies. Among these modern soil animals are arthropod predators. Our knowledge of arthropod predators in Paleozoic soil ecosystems, however, is limited. Continental ichnofossils are well known from Paleozoic paleosols although many are of uncertain origin. Interpretation of these ichnofossils, including their tracemakers, the behaviors involved, and the environmental conditions that influenced their production requires the study of modern organisms. This project involved the study of the predatory arthropod, Phrynus marginemaculata or giant whip scorpion (vinegaroon), in order to describe its burrowing behaviors and resulting burrow morphologies. The animals were placed into large, sediment-filled terrariums under stable air temperature and moisture conditions for two- to three-week periods. After the animals were removed, open burrows were cast with plaster, excavated, and described. Detailed descriptions of the subsurface structures included basic architecture, bioglyphs, complexity, and tortuosity. Additional experiments were run with variations in soil composition, density, and moisture to determine thee animal’s behavioral response to different environmental conditions. The biogenic structures produced by the whip scorpions consisted of U-shaped burrows, spiraling shafts, and boxworks composed of branching, interconnected shafts and tunnels with multiple surface openings. The results of this study show that whip scorpions produce unique three dimensional biogenic structures that possess architectural and surficial properties that can be distinguished to distinguish them from the burrows of other soil organisms. Data collected from these and similar experiments can be applied to ichnofossil assemblages found in Paleozoic paleosols in order to better interpret the paleoecology of these ancient soil ecosystems. Examination of variations in trace morphology due to environmental change will also allow for the interpretation of soil consistency, soil moisture, and relative sedimentation rates.