Tetrapod tracks from the Middle/Late Triassic of the Ourika and Yagour basins (Morocco): new ichnotaxonomical data based on the Biron collection

Palaeontological prospecting organized in the Ourika and Yagour basins (Marrakech High Atlas, Morocco) in the 1980's, have yielded abundant and exquisitely preserved tetrapod tracks, some of them preserving thinly detailed skin traces (Collection Biron, Cadi Ayyad University, Marrakech, Morocco). Based on this material, diverse morphologies of tracks were described and six new ichnotaxa were erected. However, these trackways have never been reinvestigated in detail from an ichnotaxonomic point of view. Here, the Biron collection is reevaluated using modern photogrammetric imaging techniques. The fine-grained sandstone slabs bear trackways ascribed to Apatopus lineatus, Isochirotherium isp. and Rhynchosauroides isp. whose trackmakers are possible phytosaurs, crocodylian-stem archosaurs or non-crown-group archosauriforms and lepidosauromorphs/archosauromorphs, respectively. "Chirotherium atlensis", "Enigmatopus atlensis", "Hyloidichnus triasicus", "Prochirotherium triasicum", "Pseudochirotherium oukaimedensis" and "Rectilinetopus ourikensis" are considered as invalid. The palaeoichnological assemblage includes a mixture of Early to the Middle Triassic (Isochirotherium) and Late Triassic (Apatopus lineatus) tracks. This result corroborates the biostratigraphic data recently obtain from the base of the Oukakmeden Sandstone Formation, suggesting a Middle-Late Triassic age. The living environment was a semi-arid alluvial plain with ponds and ephemeral rivers.