Conulariids from the Silurian (late Telychian) Waukesha Lagerstätte, Wisconsin

The Silurian (late Telychian) Brandon Bridge Formation, Wisconsin, USA, is renowned for hosting the Waukesha Konservat-Lagerstätte, in which several rare, enigmatic constituents have received detailed taxonomic and taphonomic study. However, more common species from this deposit remain poorly described. This study provides the first systematic description of two conulariid species documented from the Waukesha Konservat-Lagerstätte – Conularia niagarensis and Metaconularia cf. manni – and assesses their general taphonomy and preservation within this deposit. Specimens were examined using a combination of light microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy to assist in taxonomic, taphonomic and compositional analyses. Conulariid specimens display an array of preservational modes, primarily diagenetic phosphatisation and kerogenization, with minor associated pyritisation. This result suggests a taphonomic history involving post-burial demineralisation associated with falling pH conditions, subsequent compression with minimal breakage, and finally diagenetic mineralisation of the compressed thecae by francolite.美国威斯康星州志留纪晚特列奇阶（late Telychian）的布兰登布里奇组（Brandon Bridge Formation）以产出瓦乌科沙特异埋藏化石库（Waukesha Konservat-Lagerstätte）而闻名于世。该化石库中多种稀有、疑难类群已接受了细致的分类学与埋藏学研究，但该沉积层中更为常见的物种至今仍缺乏系统的描述。本研究首次对瓦乌科沙特异埋藏化石库中记录的两种锥石类（conulariid）物种——尼亚加拉锥石（Conularia niagarensis）以及相似于曼氏后锥石（Metaconularia cf. manni）——展开了系统性描述，并评估了它们在该沉积层中的一般埋藏学特征与保存模式。研究团队结合光学显微镜（light microscopy）、扫描电子显微镜（scanning electron microscopy）与能量色散X射线光谱仪（energy dispersive X-ray spectroscopy）对标本进行观测，以辅助分类学、埋藏学及成分分析工作。锥石类标本呈现出多种保存形式，主要为成岩磷酸盐化（diagenetic phosphatisation）与干酪根化（kerogenization），伴随少量黄铁矿化（pyritisation）。该结果表明，其埋藏历史涉及埋藏后期伴随酸碱度（pH）下降的去矿化作用、后续的轻微破碎压缩，以及最终由弗兰科磷钙石（francolite）对压缩后的鞘部（thecae）进行成岩矿化。