Ichnogenus Pholeus Fiege, 1944, revisited

The ichnogenus Pholeus Fiege, 1944, is a common constituent of the Lower Muschelkalk (Middle Triassic) carbonates of the Germanic Basin, where it occurs in the upper part of shallowing upward cycles. It is restricted to a marly limestone lithofacies and is commonly associated with omission and erosion surfaces. The dwelling structures (domichnia) were created in a shallow-marine to lagoonal paleoenvironment in an intertidal to shallow subtidal setting. New material from Thuringia and Lower Saxony makes a reevaluation of Pholeus possible and confirms the validity of this ichnogenus. Certain features, such as general form, wall, lining, and branching differentiate it from similar trace fossils. In addition to the already described P. abomasoformis, three new ichnospecies are named for distinctive forms: P. bifurcatus, P. platiformis, and P. elongatus. Based on geometry, size, and wall lining, the burrow producers were most probably decapod crustaceans. Many similarities to modern burrows of Callianassa sp., Neocallichirus grandimina, and Nephrops norvegicus suggest thalassinian shrimps and lobsters as likely tracemakers of Pholeus burrows. Compound burrow systems and retrusive burrow parts with spreiten-like structures are common and point to an upward shifting of the burrows related to certain sediment input in relation to tidal currents