Ordovician rhipidognathid conodonts from Australia and Iran

Abstract

Based on specimens from Australia and Iran, five species of rhipidognathid conodonts,Appalachignathus delicatulusBergström, Carnes, Ethington, Votaw, and Wigley, 1974,Bergstroemognathus extensus(Graves and Ellison, 1941),B. hubeiensisAn (MS)inAn, Chen, and Li, 1981,B. kirkiStait and Druce, 1993, andRhipidognathus?yichangensis(Ni, 1981), are described and revised in terms of multielement morphology. All three genera comprising the Rhipidognathidae are interpreted as having a septimembrate apparatus, partially confirmed by bedding plane assemblages ofB. extensusfrom Victoria. Occurrence ofA. delicatulusin allochthonous limestones (about the Middle-Upper Ordovician boundary) of central New South Wales is the first record of the species outside North America. Recognition ofRhipidognathus?yichangensisin Early Ordovician strata of the Canning Basin, reinforces biogeographic affinities of Australia and South China. The three described species ofBergstroemognathusare mainly restricted to late Early Ordovician strata.Bergstroemognathus extensusis widely distributed in North America, western Argentina (Precordillera), China, and Australia.Bergstroemognathus hubeiensis, described from east-central Iran, has been previously recorded only from China, while the slightly youngerB. kirkiseems endemic to central and northern Australia, where it was restricted to shallow, warm water environments. In contrast,B. extensusandB. hubeiensisinhabited a spectrum of water depths from shallow to deep.