Revision of conodont genus Protoprioniodus and its type species from the Lower Ordovician of the Canning Basin, Western Australia

Abstract

Examination of the original types and abundant topotype specimens from the Emanuel Formation (Early Ordovician) and the correlative subsurface Nambeet Formation of the Canning Basin in Western Australia confirms a septimembrate species apparatus for Protoprioniodus simplicissimus, the type species of the genus. Species of Protoprioniodus are characterized by having a seximembrate or septimembrate protoramiform–protopectiniform apparatus with a distinctive basal surface well-developed between the basal margin and the basal flange in the constituent elements. The generic concept of Protoprioniodus is re-defined based on its type species and reassessment of all the species previously assigned to this genus. Protoprioniodus might be evolved in late Tremadocian (Early Ordovician) possibly from an unknown species of basal Oistodus. With five species confirmatively assigned to, Protoprioniodus is recognized as a morphologically distinctive conodont clade within family Oistodontidae and biostratigraphically useful for correlation of the uppermost Tremadocian to Middle Ordovician rocks. Protoprioniodus simplicissimus was cosmopolitan while other species seem variably restricted in palaeogeographic distribution.