NEOICHNOLOGY OF SCARAB BEETLE LARVAE: MODERN ANALOGUES FOR BACKFILLED TRACE FOSSILS

Previous research has understated the ability of terrestrial organisms to significantly bioturbate continental deposits and subaerially exposed sediments. Here we describe laboratory experiments designed to understand better the burrowing abilities, mechanisms, and burrow morphologies of modern scarab beetle larvae (Cyclocephala sp.), with the goal of comparing these structures to those found in the fossil record. Insects were placed in narrow enclosures containing laminated moist sand and were allowed to burrow for a period of several weeks. Traces produced are recognizably different from previously described fluvial traces, and are characterized by subvertical, tortuous axes and discrete packets of meniscate backfill. Thickness of individual backfill segments is shown to be directly proportional to lamination thickness. Overall bioturbation patterns and individual traces produced by these organisms are similar to adhesive meniscate burrows (AMBs) found in Lower Permian eolian deposits which form part of the Hugoton Gas Field in western Kansas. It is hypothesized that Permian tracemakers had similar body plans to Cyclocephala larvae and were also likely insect larvae. Results of this and other, similar neoichnological experiments on terrestrial organisms will aid in the interpretation of depositional environments, and underscore the need to reevaluate environments originally described as subaqueous in origin.