Brasilichnium-like tracks from the Lower Triassic of the Holy Cross Mountains, Poland

摘要

This paper describes an assemblage of minute tracks preserved on a slab of sandstone from the Lower Triassic Tumlin Sandstone (Holy Cross Mountains, Poland). The slab surface of 766.9 cm(2) is covered with numerous tracks differing in size and preservation (n = 1087). Calculated track density is similar to 1.4 track/cm(2). The size of individual tracks ranges from 0.19 to 94.8 mm(2). Smaller tracks are preserved as indistinct depressions. Locally, they display a linear arrangement and may represent invertebrate trackways or vertebrate undertracks (inconclusive). Larger tracks show more details and most probably were produced by vertebrates. Locally, sets of manual and pedal imprints are observed, the pedal ones are larger. The well-preserved pedal imprints comprise a broad "heel" area and four relatively short digital imprints. Trackways are diff cult to discern due to a high number of tracks. Digital techniques of visualization are used as an aid in track pattern recognition. Small synapsids were the likely trackmakers. The tracks resemble Brasilichnium ichnogenus in terms of track morphology, pes-manus size difference, pes pace angulation and environmental settings. However, the Tumlin Sandstone tracks are Early Triassic, whereas Brasilichnium is Late Triassic-Early Jurassic and Early Cretaceous in age. Predecessors of Brasilichnium tracemakers could have produced the described tracks.