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 ha...本研究报道了目前已知最古老的造礁轴海绵科（Anthaspidellidae）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（Zhangxia Formation）的寒武系第三统（Cambrian Series 3，第5阶晚期—古丈阶早期）地层。张夏兰肯海绵主要赋存于附枝藻-兰肯海绵-寒武杯海绵（Epiphyton-Rankenella-Cambroctoconus）礁体中，少量见于礁间粒灰岩（inter-reef grainstone）。该种具有轴海绵科型规则梯状骨针网络，由树状骨簇（dendroclones）与横肋（trabs）构成，其特征为横肋平行/近平行于胃面（gastral surface），并向外延伸交汇于表皮面（dermal surface），这也是该属的典型特征。对比分别发现于澳大利亚寒武系第二统（Cambrian Series 2）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（Furongian）早期的R. hamdii，张夏兰肯海绵的鉴别特征为体壁相对更厚、表皮面与相交横肋夹角约90°，且分化管腔较为少见。另一方面……