长期以来，双壳类研究者虽未将扬于蛤(Yangtzedonta Yu)纳入到双壳类早期系统演化的研究范畴，支却又难以予以完全否定。最近，钱逸的工作终于解决了这一悬案，这是寒武纪带壳软体动物研究的一项重要进展。然而，钱逸对双壳类早期演化的理解仍存在着误解，例如，将Xianfengoconcha Zhang当作是“最古老的双壳类”，为此有必要对近二十年来我国寒武纪双壳类的研究进行回顾与总结。Xianfengoconcha发育有两侧对称排列的所谓“片状齿”，实属腕足类小圆货贝型铰合构造。化石证据表明，真正的片状齿是由古栉齿型铰齿演化而来，因此，古异齿型不是双壳类最古老的铰齿类型。目前，我国没有争议的寒武纪双壳类只有．Pojetaia Jell一属。

The genus Yangtzedonta Yu,1985 have not been accepted by bivalve specialists as a bivalve as Yu originally reported in studying early phylogeny and evolution of the class Bivalvia. Recently, Qian Yi(2001) solved this puzzle. He confirms that Y.primitiva Yu is only an incomplete specimen of Xianfengella prima He et Yang, a problematical small shelly fossil. It is a pity that Qian confused Xianfengoconcha elliptica Zhang with the oldest certain bivalve. It is necessary to review comprehensively the study of Cambrian bivalves in China. Xiangfengoconcha Zhang,1980 shows an elongate, weakly inclined anterior and posterior toothlike structure on each side of the beak. This is an obolellid-type hinge structure rather than the bivalve palaeoheterodont type. Moreover lamellar teeth of palaeoheterodonts were derived from the fusion of discrete teeth of palaeotaxodont type. Therefore, it is unlikely that the most primitive bivalve was such a form with lamellar teeth as Xianfengoconcha elliptica Zhang. At present, Pojetaia Jell, 1980 is the only undoubted Cambrian bivalve in China.

Q915.817.4

国家重点基础研究发展规划项目 (G2 0 0 0 0 7770 8)，中国科学院古生物与古人类学科基础研究特别支持费 (No .0 0 0 3 0 3 )资助课题