Three-dimensionally preserved Ediacaran fossils occur globally within sandstone beds. Sandy siliciclastic deposits of the Ediacaran Wood Canyon Formation (WCF) in the Montgomery Mountains, Nevada, contain two fossil morphologies with similar shapes and sizes: one exhibits mm-scale ridges and a distinct lower boundary and the other is devoid of these diagnostic features. We interpret these as taphomorphs of erniettomorphs, soft-bodied organisms with uncertain taxonomic affinities. We explore the cast-and-mould preservation of both taphomorphs by petrography, Raman spectroscopy, X-ray fluorescence microprobe and X-ray diffraction. All fossils and the surrounding sedimentary matrix contain quartz grains, iron-rich chlorite and muscovite. The ridged fossils contain about 70% larger quartz grains compared to the ridgeless taphomorph, indicating a lower abundance of clay minerals in the ridged fossil. Chlorite and muscovite likely originated from smectite and kaolinite precursors that underwent lower greenschist facies metamorphism. Kaolinite and smectite are inferred to have been abundant in sediments around the ridged fossil, which enabled the preservation of a continuous, distinct, clay- and kerogen-rich bottom boundary. The prevalence of quartz in the ridged fossils of the WCF and in erniettomorphs from other localities also suggests a role for this mineral in three-dimensional preservation of erniettomorphs in sandstone and siltstone deposits.

三维保存的埃迪卡拉化石遍布全球的砂岩层中。内华达州蒙哥马利山脉埃迪卡拉木峡谷组 (WCF) 的砂质硅质碎屑沉积物包含两种形状和大小相似的化石形态：一种具有毫米级的山脊和明显的下边界，另一种则缺乏这些诊断特征。我们将它们解释为erniettomorphs的taphomorphs，一种具有不确定的分类学亲和力的软体生物。我们通过岩相学、拉曼光谱、X 射线荧光探针和 X 射线衍射探索了这两种锥体的铸模保存。所有化石和周围的沉积基质都含有石英颗粒、富铁绿泥石和白云母。与无脊的锥状化石相比，有脊的化石含有约 70% 较大的石英颗粒，这表明有脊的化石中粘土矿物的丰度较低。绿泥石和白云母可能起源于经历了较低绿片岩相变质作用的蒙皂石和高岭石前体。据推断，脊状化石周围的沉积物中富含高岭石和蒙脱石，这使得能够保存连续、独特、富含粘土和干酪根的底部边界。石英在 WCF 的脊状化石和来自其他地区的 erniettomorphs 中的普遍存在也表明了这种矿物在砂岩和粉砂岩沉积物中 erniettomorphs 的三维保存中的作用。