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Paleontological Research
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Abstract
Abstract.
The apparatuses of Triassic ellisonid conodonts: Cornudina breviramulis, Hadrodontina aequabilis, and Staeschegnathus perrii gen. et sp. nov. from the Taho Formation in Higashiuwa-gun, Ehime Prefecture, Southwest Japan and Furnishius triserratus from the Iwai Formation in Nishitama-gun, Tokyo were reconstructed on the basis of the multielement structure of natural assemblages previously reported. Ellisonia triassica was remarked on this occasion. These species well agree with the general septimembrate apparatus structure containing 15 elements: angulate or pastinate P1, angulate P2, breviform digyrate M, alate S0, extensiform digyrate S1 and S2, and bipennate S3 and S4 elements. Having compared the morphologic features of apparatus elements of the Ellisonidae, I propose herein the new subfamily Hadrodontinae within it. Among the Ellisonidae and other taxa of the Prioniodinina, a phylogenetic relationship is recognized only between E. triassica and Upper Devonian Hibbardella angulata. Other species of the Ellisonidae are more closely related to ozarkodinides with “ozarkodiniform” angulate P1 element than any previously reported prioniodininids with “oulodiniform” extensiform digyrate and carminate P1 elements.
My deep gratitude is expressed to Hisayoshi Igo, Emeritus Professor of Institute of Geoscience, University of Tsukuba, for critical review of the manuscript and valuable suggestions. Thanks are also due to Michael J. Orchard, Geological Survey of Canada and an annonimous reviewer for critically reading the manuscript and providing valuable comments. I thank Shungo Kawagata (Yokohama National University) for his help in preparing the photographs.
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