The latest Devonian (Famennian) phacopid trilobite Omegops from eastern Alborz, Iran

The Late Devonian (late Famennian) phacopid trilobites represented by Omegops tilabadensis sp. nov. are described and illustrated from the Khoshyeilaq Formation, eastern Alborz Mountains, North Iran. The species formed a monotaxic trilobite association inhabiting a shallow shelf together with diverse brachiopod communities dominated by the athyridides and spiriferides. Constant differences in pygidial morphology between the geographically separated Omegops species from the Middle East, Northwest China (Junggar) and West Europe plus the North African sector of Gondwana may suggest the existence of two geographically isolated Omegops lineages which diverged in pre-Strunian time. The occurrence of conodonts not older than the Bispathodus costatus Zone and the brachiopod Rhipidomella michelini gives a sufficient proof of the Strunian to early Tournaisian age of the uppermost part of the Khoshyeilaq Formation.