Two new species of 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 species consist of a septimembrate apparatus having similar M and Sd elements. T. 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 formation, T. bifidus is almost exclusively restricted to the lower part of the Honghuayuan Formation, being replaced by T. zhiyii in the middle and upper part of the formation in the most 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, and they are likely to be endemic to this region.