Taphonomy of tiny tetrapod tracks in an example from the Lower Permian (Cisuralian) Slupiec Formation (SW Poland)

The continental Lower Permian SlLupiec Formation (the Sudetes Mountains, southwestern Poland) is well known for the occurrence of fossilized tracks of Early Permian tetrapods. Previous reports have focused on the taxonomy of tracks and their producers. The track assemblage was apparently missing the footprints of amphibians and thus such tetrapods were thought to be truly absent in the SlLupiec Early Permian paleohabitat. The present paper utilizes the results of experiments and field surveys in order to test a possibility that tracks of tiny tetrapods (e.g., with body mass < 9 g), including amphibians, could be missing due to taphonomic filtration. The experimental tests were performed to investigate the following: (1) the interplay between the sizes of the penetrator (representation of trackmaker's pes and manus) and the particles within the substrate, with emphasis on how the size interplay affects the lamina-modification mechanism, e.g., lamina-piercing by sand versus lamina compaction/displacement by sand or clay; (2) undertrack production in laminated sandy substrates by tiny tetrapods; and (3) the taphonomic impact that biofilm may have on the occurrence of tiny tetrapod tracks in clay. The results of experimental tests and the field survey suggest that tiny tetrapod tracks (e.g., amphibians) may be underrepresented in the SlLupiec Formation track assemblage due to negative taphonomic filtration.