LATE DEVONIAN CONICHNUS FROM TIOGA, PENNSYLVANIA: EVIDENCE OF ASEXUAL SEA ANEMONE REPRODUCTION

A long section of Famennian (Late Devonian) strata along US Route 15 in Tioga, Pennsylvania exposes the transition between the shallow marine Lock Haven Formation and the terrestrial Catskill Formation. Numerous specimens of the ichnofossil Conichnus have been found in the transitional zone between these facies. These conical, lined burrows are typically interpreted as dwelling or resting traces of sea anemones. Different aspects of the burrows’ structure are visible on the tops, soles, and sides of beds. Sedimentary structures in this interval include mudcracks and microbial fabrics, and adjacent beds contain Skolithos. The Conichnus-bearing interval contains a few beds with low-diversity body fossil assemblages (e.g., lingulids and Cyrtospirifer), in contrast with the base of the section, which possesses a diverse marine fauna (primarily brachiopods). The Conichnus of Tioga are smaller than many occurrences described previously (diameter equals 4.5-9.5 mm, height equals 3+ times the diameter, where visible). Other, less well-preserved cnidarian ichnofossils (e.g., Bergaueria) have been described elsewhere in the Upper Devonian Appalachian Basin. Thus, sea anemones were not uncommon along the shores of the Catskill Sea. The Tioga specimens show interesting features such as disturbed laminae (equilibrium structures) representing adjustment by the sea anemones to background sedimentation. The trace makers were also able to exhume and reposition themselves after significant depositional events (several cm of sediment, equivalent to the depth of the trace). In some specimens, the burrows are aligned in chains, possibly representing asexual reproduction by binary fission.