中文摘要：

对中国早寒武世软体动物腹足类标本的再研究表明，早期腹足类Archaeospiriids，Auriculaspiriids和Xinjispiriids无一例外都以开放松旋型初始壳（胎壳）为特征，但这些腹足类的胎壳与后续螺壳的分界各具标志。这种胎壳是古生代腹足类特有的特征。研究结果证明，以开放松旋型初始壳为特征的腹足类胎壳可以追溯到早寒武世的梅树村期。这种开放松旋型胎壳的特征使一直以来颇受争议的Archae。spiriids和Auriculaspiriids是否归属于腹足类得到了肯定。梅树村期的Archaeospiriids胎壳直径在200—250μm之间，表明其幼体是一种非漂浮营养型的生活模式，而沧浪铺期的Auriculaspiriids和Xinjispiriids胎壳直径均小于130μm，其幼体可能是一种漂浮营养型的生活模式。因此，早期腹足类首先选择的是非漂浮营养型的幼体生活模式，而从发育非漂浮营养型的幼体生活模式到发育漂浮营养型的幼体生活模式，这种多样性的变化可能在寒武纪大爆发主幕阶段就已呈现。实现腹足类幼体生活模式多样化的因素除了捕食作用产生的生物竞争压力所诱导的逃逸本能外，动荡的水动力环境和由此引起的营养悬浮物进一步增加可能是促使早期腹足类幼体生活模式发生根本性变化的重要因素。

英文摘要：

Further research on gastropod fossils of the Early Cambrian, China shows that early gastropod Archae- ospiriids, Auriculaspiriids and Xinjispiriids are all characterized by openly coiled initial whorls （protoconch）, but their protoconchs are distinguished by typical marks from the successive whorls. The openly coiled initial whorls are speci- fic for the Paleozoic gastropods. This research demonstrates that gastropod protoconch with the openly coiled initial whorls may be traced into the Meishucunian Stage of the earliest Cambrian, instead of the previous Atdabanian Stage （equal to Qiongzhusian Stage） of the Early Cambrian. This study demonstrates that Archaeospiriids and Auricu- laspiriids are gastropod affiliation. The Meishucunian Archaeospiriid protoconchs of the Cambrian are generally 200--250 /~m in diameter, implying a larval development with nonplanktotrophic, while the Canglangpuian Auriculaspiriid and Xinjispiriid protoconchs of the Cambrian are commonly less than 130 ~m, meaning a larval development with planktotrophic. Therefore, early gastropods likely first selected a nonplanktotrophic larval development mode,and evo- lution from nonplanktotrophic to planktotrophic larval developments possibly occurred during the Early Cambrian, equal to the main stage of Cambrian explosion represented by the Chenjiang Fauna. In addition to predation-driven escalation, fundamental factors impelling the change also lies in an increasing nutrient supply and availability of photoautotrophic plankton in oceans.