Middle Devonian ichnofossils from Hamar Laghdad (eastern Anti-Atlas, Morocco)

This article provides a description of the invertebrate trace fossils from the Hamar Laghdad region of Tafilalt in Morocco. These ichnoassemblages occur in Middle Devonian marly limestone layers, which are characterised by varying clastic content and different degrees of dolomitisation. These Eifelian and Givetian ichnoassemblages comprise: (i) Eifilian ichnoassemblages consisting of Arenicolites isp., Crescentichnus antarcticus, Selenichnites hundalensis and Osculichnus cf. labialis; (ii) a Givetian ichnoassemblage containing Arenicolites isp., Diplocraterion isp., Sinusichnus sinuosus, and Thalassinoides paradoxicus. The Eifelian strata were deposited in a moderately shallow inner shelf environment, which have been changed to a deeper inner shelf setting during the Givetian. This environment was characterised by high energy levels and a high concentration of organic matter. Some of these ichnotaxa are commonly referred to feeding of xiphosurans or trilobites, traces of suspension feeding and dwellings of polychaete worms and crustaceans, deposit-feeding non-decapod crustaceans, as well as deposit-feeding and dwelling of crustaceans. The present comprehensive ichnological analysis is important in at least three aspects: (1) it reports the oldest occurrences of Selenichnites and Sinusichnus in Africa and one of the oldest in the world; (2) It suggests a more ancient root for the represented complex behaviour of modern arthropods than previously thought; (3) It contributes to the understanding of the environmental deposit settings. The great palaeobiodiversity of Hamar Laghdad includes not only the skeletal record, but also ichnofossils. Both records indicate regional favourable environmental settings, characterised by local topography that varied over time and space, formed by several cold and hydrothermal seeps combined with sea-level fluctuations and currents.