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.

本研究报道了目前已知最早的造礁柔海绵科（anthaspidellid）海绵新种——张夏兰肯海绵（Rankenella zhangxianensis n. sp.），其化石产自中国山东省张夏组寒武系第三统（第5阶晚期—古丈阶早期）地层。张夏兰肯海绵主要产出在附植藻（Epiphyton）-兰肯海绵（Rankenella）-坎伯洛锥壳（Cambroctoconus）礁体中，少量见于礁间颗粒灰岩地层。该种具有柔海绵科典型的规则梯状骨针网，由树状克隆骨针（dendroclones）和横棒（trabs）构成；其特征为横棒与胃面平行或近于平行，呈发散状延伸并与皮面相接，这也是该属的典型特征。相较于分别产自澳大利亚寒武系第二统晚期—寒武系第三统晚期的R. mors和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，皮面与相交横棒之间的夹角较大（约90°），且分化管腔的发育程度较低。另一方面，张夏兰肯海绵整体呈倒锥形，形态多样性远低于另外两种，后者分别呈锥圆柱形、指状、平展状或碗状。这些产自中国的寒武系第三统礁体，是全球繁盛的芙蓉统柔海绵科-微生物礁体以及早奥陶世柔海绵科-微生物礁体的祖先类群。它们代表了寒武系第二统末古杯动物（archaeocyaths）灭绝之后，造礁后生动物的复苏事件。