First occurrence of a Middle Triassic tetrapod ichnofauna from the Argana Basin (Western High Atlas, Morocco)

Abstract

Footprints of Early Mesozoic terrestrial tetrapods are inadequately known from NW Africa despite pervasive and well-exposed continental strata of corresponding age in that region. Here, we report on the first occurrence of a tetrapod ichnofauna from the middle part of the Triassic Timezgadiouine Formation in the Argana Basin, Central Morocco that is outstanding in terms of abundance, preservation, and diversity. Footprints of this assemblage are assigned to the ichnotaxa Chirotherium barthii, Isochirotherium coureli, Synaptichnium isp., Atreipus–Grallator, Rotodactylus isp., Rhynchosauroides isp., and Procolophonichnium isp., suggesting early archosaurian, dinosauromorph, lepidosauromorph and possible therapsid or procolophonoid trackmakers. Based on comparison with the abundant record of Early Mesozoic vertebrate ichnofossils from Europe and North America, the ichnofauna presented here indicates a Middle Triassic (Anisian–Ladinian) age for the track-bearing horizon in the Argana Basin. Its clearly Euramerican affinity sheds light on the migration and dispersal of early archosaur-dominated tetrapod faunas considering that several ichnotaxa of the assemblage are documented from Africa for the first time.