Early Ordovician Triangulodus (Conodonta) from the Honghuayuan Formation of Guizhou, South China

Abstract

Two new conodont species, Triangulodus, T. bifidus sp. nov. and T. zhiyii sp. nov., are described and illustrated from the Early Ordovician Honghuayuan Formation of Guizhou, South China. Both consist of a septimembrate apparatus having similar M and Sd elements. Triangulodus bifidus is distinguished from all other known species of Triangulodus in displaying bifurcating costae on all seven constituent elements. Although the ranges of both species overlap and extend through most of the unit, T. bifidus is more abundant in the lower part of the Honghuayuan Formation, whereas T. zhiyii is most common in the middle and upper part of the formation in the more comprehensively sampled type section. Both new species are widely distributed in South China, with T. bifidus also reported in the Lower Ordovician of the Tarim Basin.