Psammichnites from the Pennsylvanian Rod El-Hamal Formation of Egypt: revisiting paleoenvironmental and paleogeographic patterns of distribution of late Paleozoic ichnospecies

The occurrence of the ichnogenus Psammichnites from the Pennsylvanian Rod El-Hamal Formation, Wadi Araba, Eastern Desert of Egypt, represents its first record in Africa. Specimens occur mostly on rippled troughs of a sandstone layer deposited in an offshore transition setting. This ichnogenus is characterized by sinuous to looped, backfilled trails that are present most commonly in positive epirelief and are marked by a distinctive median dorsal structure. Densities are among the highest recorded so far for this ichnotaxon, reaching coverage of circa 45–50% on bed surfaces (Bedding Plane Bioturbation Index [BPBI] 4–5). Three ichnospecies have been identified, in order of abundance, Psammichnites plummeri, P. grumula, and P. cf. P. implexus. A global compilation of late Paleozoic occurrences further supports the affinity of Psammichnites with marginal- and open shallow-marine environments, under brackish to normal-marine salinity conditions, respectively, instead of hypersalinity as recently proposed. Psammichnites appears to be a cosmopolitan ichnogenus showing a broad latitudinal distribution during the late Paleozoic, having been particularly widespread during the Pennsylvanian.