Ordovician rhipidognathid conodonts from Australia and Iran

Based on specimens from Australia and Iran, five species of rhipidognathid conodonts, Appalachignathus delicatulus Bergstrom, Carnes. Ethington. Votaw , and Wigley, 1974. Bergstroemognathus extensus (Graves and Ellison, 1941), B. hubeiensis An (MS) in An, Chen. and Li. 1981. B. kirki Stair and Druce. 1993. and Rhipidognathus? vichangensis (Ni, 1981). are described and revis ed in terms of multielement morphology. All three genera comprising the Rhi pidopnathidae are interpreted as having a septimembrate apparatus. partiall y confirmed by bedding plane assemblages of B. extensus from Victoria. Occu rrence of A. delicatulus in allochthonous limestones (about the Middle-Uppe r Ordovician boundary) of central New South Wales is the first record of th e species outside North America. Recognition of Rhipidognathus? yichangensi s in Early Ordovician strata of the Canning Basin, reinforces biogeographic affinities of Australia and South China. The three described species of Be rgstroemognathus are mainly restricted to late Early Ordovician strata. Ber gstroemognathus extensus is widely distributed in North America, western Ar gentina (Precordillera), China, and Australia. Bergstroemognathus hubeiensi s, described from east-central Iran, has been previously recorded only from China, while the slightly younger B. kirki seems endemic to central and no rthern Australia. where it was restricted to shallow, warm water environmen ts. In contrast. B. extensus and B. hubeiensis inhabited a spectrum of wate r depths from shallow to deep.