Ordovician trilobites from the Tafilalt Lagerstatte: new data and reappraisal of the Bou Nemrou assemblage

The early Late Ordovician (Sandbian 1) representatives of the Tafilalt Biota in the locality of Bou Nemrou (Jbel Tjarfaiouine) provide examples of fossil preservation in medium-grained sandstones with abundant microbially induced sedimentary structures. The recorded trilobite assemblage comprises 11 species of ten genera, among which one is new (Placoparia africana Pereira & Gutierrez-Marco, sp. nov.) and four others previously regarded as endemic to the locality are considered to be synonymys of species already described from Bohemia. The oldest representative of the illaenid genus Cekovia is recorded, revised diagnosis proposed for the genus Mytocephala Struve and for Uralichas tardus Vela & Corbacho. Parvilichas Corbacho & Vela is considered to be a junior synonym of Uralichas Delgado. From a palaeobiogeographical point of view, the Bou Nemrou locality shows strong relationships with trilobite assemblages from the Dobrotivian and with the lower Berounian sandstone facies of Bohemia, reinforcing the correlation of both regions. Some soft-bodied structures are recognized here, including the digestive tracts of Uralichas and the traces of paired, metameric axial bands in the anterior thoracic segments of the trilobite Selenopeltis preserved in apatite and interpreted as intersegmental musculature.