Annelids from the Cambrian (Wuliuan Stage, Miaolingian) Spence Shale Lagerstätte of northern Utah, USA

The Spence Shale Member of the Langston Formation in northern Utah and southern Idaho preserves generally non-biomineralized fossil assemblages referred to as the Spence Shale Lagerstätte. The biota of this Lagerstätte is dominated by panarthropods, both biomineralized and soft-bodied examples, but also preserves diverse infaunal organisms, including species of scalidophorans, echinoderms, lobopodians, stalked filter feeders, and various problematic taxa. To date, however, only a single annelid fossil, originally assigned to <i>Canadia</i> sp., has been described from the Spence Shale. This lone specimen and another recently collected specimen were analysed in this study using scanning electron microscopy and energy dispersive X-ray spectrometry. The previous occurrence was reassigned to <i>Burgessochaeta</i> cf. <i>B. setigera</i>. The new fossil, however, has been identified as a novel polychaete taxon, <i>Shaihuludia shurikeni</i> gen. et sp. nov., characterised by the presence of fused, bladed chaetae and a wide body. The occurrence of <i>Burgessochaeta</i> is the first outside the Burgess Shale and its vicinity, whereas <i>Shaihuludia shurikeni</i> gen. et sp. nov. adds to the diversity of annelids in the middle Cambrian and highlights the diversity of the Spence Shale Lagerstätte.

犹他州北部与爱达荷州南部的兰斯顿组（Langston Formation）斯彭斯页岩段（Spence Shale Member）产出了以斯彭斯页岩化石库（Spence Shale Lagerstätte）为代表的典型非矿化化石组合。该化石库的生物群以泛节肢动物（panarthropods）为优势类群，涵盖矿化类群与软躯体类群，同时保存有丰富的内生底栖生物类群，包括动吻动物类（scalidophorans）、棘皮动物（echinoderms）、叶足动物（lobopodians）、柄状滤食生物以及多种疑难分类单元。但截至目前，斯彭斯页岩中仅报道过1枚环节动物化石，其最初被归为加拿大虫属（*Canadia*）sp.。本研究针对这枚孤本标本与另一枚新近采集的标本，采用扫描电子显微镜与能量色散X射线能谱仪开展了分析测试。此前的标本被重新归为伯吉斯沙蚕属（*Burgessochaeta*）cf. *B. setigera*；而新发现的化石则被鉴定为一个全新的多毛类分类群——新属新种*Shaihuludia shurikeni* gen. et sp. nov.，其鉴别特征为具有愈合的刃状刚毛与宽阔的躯体。伯吉斯沙蚕属（*Burgessochaeta*）的此次发现是该属首次在伯吉斯页岩及其周边区域之外被报道；新属新种*Shaihuludia shurikeni* gen. et sp. nov.则丰富了中寒武世环节动物的多样性，并进一步凸显了斯彭斯页岩化石库的生物多样性。