The holotype of Yangtzedonta Yu, 1985 and itstype species, Y. primitiva Yu, 1985, is an incomplete specimenof Xianfengella prima He et Yang, 1982. Therefore, based onthe principle of priority, the names Yangtzedonta and Y.primitiva Yu (1985) should be abandoned. The fact that ven-tral valve of Xianfengella is bilaterally symmetrical indicatesthat they are not the left valve of a bivalved mollusc, asoriginally proposed by Yu. At present, the oldest certain bi-valve is Xianfengoconcha elliptica Zhang, which occurs in theEarly Cambrian Qiongzhusi Stage in China. The oldestknown rostroconch is Heraultipegma yunnanensis He et Yang,which first occurs in the third small shelly fossil assemblagezone of the Early Cambrian Meishucunian Stage. The oldestknown monoplacophoran, Maikhanella pristinis (Jiang), firstoccurs in the first small shelly fossil assemblage zone (Me-ishucunian Stage). Evidence derived from analyses of shellmorphology, mode of growth, histology, and stratigraphicoccurrence suggests that bivalves evolved from a branch ofrostroconchs, and that rostroconchs in turn evolved from abranch of monoplacophorans. The hypothesis that thesethree groups originated simultaneously and independently atthe beginning of the Cambrian and subsequently evolved inparallel, probably is incorrect.