Tunnel-and-Chamber Burrows: Evidence for Fossorial Behavior of Insects in Permo-Carboniferous Alluvial-Plain Deposits?

Hitherto undescribed medium-sized burrows are recognized as a common element of Late Carboniferous to Early Permian alluvial-plain deposits. The simply constructed trace fossils consist of unornamented to longitudinally striated tunnels terminating in ovoid chambers. Tunnel segments may be 1 to 26 mm in diameter and up to 2.5 m long. They run predominantly horizontally or subhorizontally without branching. Mud-lined walls and a passive burrow fill indicate a dwelling trace probably excavated in subaerially exposed sediments. Size, architecture, and surface morphology, as well as habitat constraints of the trace fossils, are most similar to burrows of extant insects living partially or permanently underground. The wide distribution of the fossil traces is indicative of fossorial organisms, being significant for late Paleozoic terrestrial ecosystems. Records come from seven different basins from the Western United States to Eastern Europe, all situated in the tropical belt of the Pangea supercontinent during Permo-Carboniferous times. The featured burrows are not only a stimulus to search for ichnofossils in well-drained late Paleozoic continental deposits, but also evidence for ecospace utilization by rapidly radiating insects in that period.