LATEST EARLY TO EARLY MIDDLE DEVONIAN TRILOBITES FROM THE ERBENOCHILE BED, JBEL ISSOUMOUR, SOUTHEASTERN MOROCCO

A bed on Jbel Issoumour, near Alnif in southeastern Morocco, contains numerous complete trilobites. The bed is located stratigraphically at the base of the El Otfal Formation, immediately above a cliff-forming resistant unit known to local trilobite miners as the 'grand calcaire', and is latest Emsian or early Eifelian in age. The fauna exhibits an alpha trilobite diversity of at least eight species, including Erbenochile issoumourensis n. sp., Acanthopyge (Lobopyge) bassei n. sp., and Walliserops lindoei n. sp. The absence of lateral palpebral extensions in E. issoumourensis but their presence in the type species of Erbenochile, E. erbeni, when considered with other differences in the exceptionally large eyes of both species, supports the hypothesis that these palpebral structures functioned as eyeshades in E. erbeni but not in E. issoumourensis. Walliserops lindoei has a short, stout haft at the base of the trident anterior cephalic projection, which is the most characteristic feature of Walliserops. This projection in Walliserops primarily functioned as a deterrent to predators.