Large Complex Burrows of Terrestrial Invertebrates: Neoichnology of Pandinus imperator (Scorpiones: Scorpionidae)

Abstract

Scorpions have comprised a significant portion of the diversity of predatory arthropods since the Late Paleozoic. Many of these animals are active burrowers today and likely have a substantial, if yet unrecognized, trace fossil record. This project involved the study of the burrowing behavior and biogenic structures of the scorpion Pandinus imperator (Scorpiones: Scorpionidae). Individuals and groups of five animals were placed into sediment-filled terrariums for 30–50 days after which the open burrows were cast and described. Additional experiments were conducted in sediments with two different moisture contents to evaluate the response to this altered environmental condition. Specimens of Pandinus imperator excavated their burrows using the first three pairs of walking legs. The burrow morphologies produced consisted of subvertical ramps, helical burrows, and branching burrows. The burrow elements were elliptical in cross section (12 cm wide × 4 cm high) with concave floors and ceilings. Decreased sediment moisture reduced the complexity of the subsurface structures and reduced the likelihood of their preservation due to gravitational collapse. Burrows of Pandinus imperator were compared to those of the desert scorpion, Hadrurus arizonensis, using nonparametric statistics and found to be distinct. Data collected from these and similar neoichnological studies can be applied directly to interpret trace fossil assemblages found in continental paleoenvironments.