Knowledge of Cambrian animal anatomy is limited by preservational processes that result in compaction, size bias, and incompleteness. We documented pristine three-dimensional (3D) anatomy of trilobites fossilized through rapid ash burial from a pyroclastic flow entering a shallow marine environment. Cambrian ellipsocephaloid trilobites from Morocco are articulated and undistorted, revealing exquisite details of the appendages and digestive system. Previously unknown anatomy includes a soft-tissue labrum attached to the hypostome, a slit-like mouth, and distinctive cephalic feeding appendages. Our findings resolve controversy over whether the trilobite hypostome is the labrum or incorporates it and establish crown-group euarthropod homologies in trilobites. This occurrence of moldic fossils with 3D soft parts highlights volcanic ash deposits in marine settings as an underexplored source for exceptionally preserved organisms.

中文翻译：

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快速火山灰埋葬揭示了寒武纪三叶虫的 3D 解剖结构


寒武纪动物解剖学知识受到保存过程的限制，导致压缩、尺寸偏差和不完整。我们记录了三叶虫的原始三维 (3D) 解剖结构，这些三叶虫是通过进入浅海环境的火山碎屑流的快速灰烬掩埋而形成化石的。来自摩洛哥的寒武纪椭圆头状三叶虫关节清晰，未变形，揭示了附肢和消化系统的精致细节。以前未知的解剖结构包括附着在下唇上的软组织盂唇、狭缝状的嘴和独特的头侧进食附属物。我们的研究结果解决了关于三叶虫下口是否是盂唇或包含它的争议，并建立了三叶虫冠群真节肢动物的同源性。这种具有 3D 软部件的模化石的出现凸显了海洋环境中的火山灰沉积物是保存完好的生物体的未经充分探索的来源。