The existing information on the Ordovician conodont faunas from the East-Central Iranian Platform is poor and mostly confined to the Tremadocian and Darriwilian time intervals. The study of the Lower Ordovician succession exposed at Kuh-e-Asheghan (Kalmards Block) west of the town of Tabas, provides the first record of the occurrence of Floian conodonts in the whole region. A moderately rich conodont assemblage, including Trapezognathus diprion (Lindström), Gothodus costulatus Lindström, Drepanoistodus forceps (Lindström), Drepanoistodus basiovalis Sergeeva, Protopanderodus rectus (Lindström), Drepanodus arcuatus Pander and Erraticodon patu Cooper, has been recovered from the carbonate unit in the upper part of the mainly siliciclastic succession, provisionally referred to the Katekoyeh Formation. This assemblage can be assigned to the Trapezagnathus diprion Zone, presently recognised in the upper part of the Floian Stage in South China, Peru, Bolivia and Argentina and it can be also correlated with the Trapezognathus diprion Subzone in the middle part of the Oepikodus evae Zone of the Baltoscandian biozonal scale. The underlying limestone beds contain Triangolodus bifidus. This species with a narrow stratigraphical range is the eponymous taxon for the recently introduced uppermost Tremadocian Zone in South China. It also ranges up into the lower part of the Oepikodus evae Zone. The Early Ordovician (Floian) conodont fauna of East-Central Iran can be assigned to the Temperate Domain of the Shallow-Sea Realm, following the biogeographical model introduced by Zhen and Percival in 2003, with the closest similarity to the contemporaneous faunas of South China and western South America.

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