晚二叠世是否出现克氏蛤（Claraia）.是个有争议的问题,经研究认为Claraia已在晚二叠世早期出现.对假克氏蛤（Pseudoclaraia）和类克氏蛤（claraioides）属征的研究以及与Claraia的比较表明,属级特征上三者基本相同.根据命名优先律.Pseudoclaraia和claraioides应归入Claraia.华南晚二叠世Claraia生活在次深海大陆斜坡中下部的低能静水中,营表栖足丝附着、具一定游泳能力的生活方式.对克氏蛤演化关系的研究表明,三叠纪的克氏蛤是由二叠纪克氏蛤演化而来. The occurrence of Claraia in the Late Permian is a controversial issue that Claraia was thought to have occurred in the early Late Permian in the study, which is a sign of Pseudoclaraia and claraioides And Claraia showed that the three genera are basically the same, according to the nomenclature of priority.Pseudoclaraia and claraioides should be classified as Claraia. Late-Permian Claraia in South China lived in low-level hydrostatic water in the middle and lower part of the secondary deep-sea continental slope, Campanulaceae silkworm attached to a certain swimming ability of life style.Studies on the evolutionary relationship of clams revealed that Triassic clams is evolved from Permian clams.