Review of the Early to Mid Ordovician orthoconic cephalopods from Iran

Cephalopods from the late Tremadocian of the Eastern Alborz and the Darriwilian of the Eastern Alborz and Derenjal Mountains consist of relatively poorly preserved, low diversity assemblages of endocerids and orthoceratoids. Bactroceras sp. from the late Tremadocian of the Eastern Alborz is one the earliest occurrences of the genus; similar in age to those from the Montagne Noire, France, and consistent with other high latitude records during the Early Ordovician. Darriwilian taxa consist of an unnamed troedssonellid previously recorded from Sweden, three taxa ascribed to Virgoceras Flower, Sactorthoceras sp. and Gangshanoceras? sp. By comparison with the coeval cephalopod faunas of South China and Baltica, those described here are of very low diversity, but are common to both areas. Darriwilian cephalopod assemblages from other parts of high latitude peri-Gondwana remain poorly known, but consist of eothinoceratids, bathmoceratids, endocerids and orthoceratoids. The Iranian faunas provide a glimpse of the generic composition of part this high latitude assemblage, and indicate clear links with those of South China and Baltic.