海豆芽——进化中的“活化石”*

舌形贝（Lingulidae）最早出现在寒武纪早期，因其壳体外形与现代舌形贝相似，通常被认为是活化石，但形态解剖研究表明澄江化石库舌形贝属Lingulella 和Lingulellotreta 与现代舌形贝Lingula在脉管系统、刚毛排列和内脏区分布，以及生活方式方面存在较大差别，进而表明了“活化石”在漫长的地质历史中也存在一定的环境适应性改变。

Lingulids: the Evolutionary "Living Fossils"

Lingulids（Lingulidae）made their first appearance in the Early Cambrian, which are ordinarily considered as one of the most ancient “living fossils” based on the characteristic shell shape and the supposed absence of morpho anatomical changes. Comparison between the morpho anatomical characters of the Early Cambrian Lingulide Lingulella chengjiangensis and Lingulellotreta malongensis from the Chengjiang Lagersttte of southern China, does little to support the widespread notion that the morphology of the lineage has remained remarkably constant since their first occurrence.