UPPER DEVONIAN CRAWLING TRACE PRODUCED BY LOBE-FINNED FISH, CATSKILL FORMATION, WYALUSING, PA

A large crawling trace, located on the bedding plane of a medium-grained, light reddish-gray channel sandstone at Wyalusing Rocks, Bradford County, PA, may have been produced by an Upper Devonian lobe-fin fish. The trace (up to 16 cm wide and 284 cm long) consists of a central grooved ridge with fine curved lobe-like impressions extending from its margins. The fish that made it may have used its pectoral lobe-fins to push into the sediment, creating the lobe-like impressions, while its anal fin or tail scraped into the sediment producing the grooved ridge. Small interference ripples and the trace Rivularites, which are cross cut by the crawling trace, suggest the presence of shallow water that allowed the fish to remain semi-buoyant while moving across the soft sediment. In addition to the fish trace, the lower jaw and part of the head of Hyneria (tentatively identified), a carnivorous Crossopterygian fish, and a well articulated placoderm, Bothriolepis, was also found.

This succession of red terrestrial deposits, presently mapped as occurring near the base of the Catskill Formation, represents a tidally influenced, marginal-marine environment, exposed during periods of water level fluctuation, probably related to high sedimentation. The presence of Eospermatoperis, Archaeopteris, and other plant traces, raindrop impressions, crawling traces, and mudcracks provides greater evidence for periodic subaerial exposure. Because both Hyneria and Eospermatoperis have been previously found in marginal-marine deposits, it is possible that this environment was influenced by brackish water.

This study introduces a new crawling trace fossil, possibly produced by a lobe-fin fish. It also provides a paleoenvironmental description of terrestrial deposits that may help differentiate some of the undivided Upper Devonian rock of northeastern PA.