Non-tetrapod trace fossils from the Middle Devonian tetrapod tracksite at Zachełmie Quarry, Holy Cross Mountains, Poland

Abstract

The Middle Devonian (Eifelian) dolomites exposed in the Zachełmie Quarry (Holy Cross Mountains, southern Poland) contain the earliest fossil record of tetrapods. Low-diversity, but unique assemblages of trace fossils characterize the track-bearing interval within the Lower Complex of the Wojciechowice Formation. The reconstructed environment of the trace fossil-rich beds includes ephemeral lakes and/or shallow-water lagoons separated from an open marine area by sparsely vegetated islands and spits. The most abundant non-tetrapod trace fossils from these beds are large, horizontal-to-vertical burrows, and dish-, circular- to oval-shaped, shallow depressions. The burrows are abundant on the upper surfaces of thick dolomicritic beds, especially in some palaeosol levels, but they are also associated with tetrapod trackways. Large, semi-aquatic or terrestrial animals (e.g., arthropods or vertebrates) most likely produced these burrows. The circular- to oval-shaped depressions observed on a large surface and other smaller, isolated blocks from the same stratigraphical level are interpreted as fish feeding/nesting/resting traces. Piscichnus sanctacrucensis isp. nov. is proposed as a new ichnospecies of the oval-shaped fish trace fossil from the Middle Devonian of Poland. A single, medium-sized Undichnia specimen, a fish swimming trace, is associated with the Piscichnus traces. The described trace fossils provide new insight into the palaeoecology and taphonomy of the Middle Devonian tetrapod tracksite from Poland and clarify remaining controversies regarding the interpretation of some poorly preserved trace fossils from the Zachełmie Quarry.