Data from: The earliest reef-building anthaspidellid sponge Rankenella zhangxianensis n. sp. from the Zhangxia Formation (Cambrian Series 3), Shandong Province, China

This study reports the earliest known reef-building anthaspidellid sponge, Rankenella zhangxianensis n. sp., from the Cambrian Series 3 (late Stage 5–early Guzhangian) deposit of the Zhangxia Formation, Shandong Province, China. Rankenella zhangxianensis mostly occurs within Epiphyton-Rankenella-Cambroctoconus reefs, with minor occurrence from inter-reef grainstone. The species has anthaspidellid-type regular ladderlike spicule networks consisting of dendroclones and trabs, and is characterized by trabs parallel/subparallel to the gastral surface that diverge and meet the dermal surface, which is typical of the genus. Compared to R. mors and R. hamdii, reported from the late Cambrian Series 2–late Cambrian Series 3 of Australia and the late Cambrian Series 3–early Furongian of Iran, respectively, R. zhangxianensis is characterized by a relatively thicker wall, high angle (~90°) between dermal surfaces and intersecting trabs, and minor occurrence of differentiated canals. On the other hand, R. zhangxianensis mainly shows obconical shape, which is far less diverse than the other two species showing conicocylindrical, digitate, explanate, or bowl shapes. These Cambrian Series 3 reefs from China are the ancestors of the Furongian anthaspidellid-microbial reefs and the Early Ordovician anthaspidellid-microbial reefs that flourished worldwide. They represent the resurgence of reef-building metazoans after the extinction of archaeocyaths at the end of Cambrian Series 2.本研究报道了已知最古老的造礁异轴海绵科（anthaspidellid）海绵——张夏兰肯海绵（Rankenella zhangxianensis n. sp.），其化石产自中国山东省寒武系第三统（第5阶晚期—古丈阶早期）张夏组地层。张夏兰肯海绵主要赋存于附植藻（Epiphyton）-兰肯海绵（Rankenella）-寒武杯海绵（Cambroctoconus）礁体中，少量见于礁间粒灰岩。该物种具有异轴海绵科典型的规则梯状骨针网，由树枝状骨针（dendroclones）与横棒骨针（trabs）构成，其特征为横棒平行或近平行于胃面，并向外延伸至外皮表面汇合，这亦是该属的典型特征。相较于分别发现于澳大利亚寒武系第二统晚期—寒武系第三统晚期的R. mors与伊朗寒武系第三统晚期—芙蓉统早期的R. hamdii，张夏兰肯海绵具有相对更厚的体壁、外皮表面与相交横棒骨针间近乎90°的高夹角，且分化出的管腔结构较少。另一方面，张夏兰肯海绵整体呈倒锥体形，而另外两个物种分别呈现锥圆柱形、指状、扁平扩展状或碗状，形态多样性远高于本种。这些产自中国寒武系第三统的礁体是芙蓉统异轴海绵-微生物礁以及全球繁盛的早奥陶世异轴海绵-微生物礁的祖先类群，它们代表了寒武系第二统末期古杯动物（archaeocyaths）灭绝后，造礁后生动物的复苏事件。