软舌螺动物是华北板块寒武系小壳化石基本组成之一, 也是寒武纪生命大爆发在华北地区的重要见证者。本文系统描述了华北板块南缘-西南缘(河南-陕西地区)寒武系第二统辛集组软舌螺化石9属14种及1未定种。包括直管螺类6属9种：Conotheca australiensis, Cupitheca holocyclata, Cupitheca costellata, Cupitheca? decollata, Tegminites hymenodes, Triplicatella disdoma, Triplicatella xinjia, Protomicrocornus triplicensis, Longxiantheca mira; 软舌螺类3属5种及1未定种: Microcornus eximius, Microcornus petilus, Parkula cf. esmeraldina, Parkula bounites, Parakorilithes mammillatus, Parakorilithes sp.。基于大量保存精美的聚合标本, 本文准确重建了锥壳和口盖在软舌螺不同属种中的配置。此外, 新材料显示华北辛集组软舌螺超过一半的属种钙质锥壳内侧发育隔板。其中, Conotheca和Longxiantheca隔板能有效加固和进一步封闭锥壳壳顶; Cupitheca和Microcornus沿隔板具断壳现象; Parakorilithes和Protomicrocornus分别发育特殊的单隔板和多隔板, 能够很大程度上避免软体组织深入锥壳内部。笔者认为软舌螺通过口盖具齿、隔板加固、锥壳断壳等方式能有效增强锥壳-口盖闭合性和钙质外骨骼对海底环境的适应性, 以及通过具触手营养器官进行滤食-腐食-掘食等不同方式生活。这些生存策略和适应性演化特征可能是软舌螺动物快速辐射并繁盛于寒武纪海洋的重要原因。
Hyoliths were one of the prominent components of the Cambrian small shelly fossil assemblage on the North China Block, and witnessed the explosive radiation of animal life in North China. Here fourteen species and one undetermined species assigned to nine genera of the Hyolitha were systematically described from the Cambrian Series 2 Xinji Formation along the south-southwestern margin of the plate. This hyolith fauna yields six orthothecid genera and nine species: Conotheca australiensis, Cupitheca holocyclata, Cupitheca costellata, Cupitheca? decollata, Tegminites hymenodes, Triplicatella disdoma, Triplicatella xinjia, Protomicrocornus triplicensis, Longxiantheca mira; three hyolithid genera and five species and one undetermined species: Microcornus eximius, Microcornus petilus, Parkula cf. esmeraldina, Parkula bounites, Parakorilithes mammillatus, Parakorilithes sp. Based on abundant well-preserved articulated specimens of this assemblage, we provided a complete reconstruction of the hyolith skeletons (conch-operculum). In addition, more than half of studied hyolith species in North China possessed transverse septa of their conch. Of these, septa in Conotheca and Longxiantheca can effectively strengthen and further seal off the apical end of the conch, and are used for decollation during growth of the conch in Cupitheca and Microcornus. Moreover, Parakorilithes and Protomicrocornus conchs develop single and multiple septa respectively, which could largely avoid penetration of soft tissues into the conical shells. According to these observations, we propose that the presence of teeth-like structures of operculum, septa and unique decollating growth mode of conch can significantly enhance the sealing of the conch by associated operculum, and improve adaptability of calcareous exoskeletons to marine substrate environments. Meanwhile, the tentacle-bearing feature of soft tissues is functioned as suspension-scavenging-detritus feeding apparatus and adapted to a wide spectrum of niches. These survival strategies and evolutionary adaptability may be one of the important reasons for the rapid diversification and thrive of hyoliths in the Cambrian ocean.