The challenge of identifying fossilized organelles has long hampered attempts to interpret the fossil record of early eukaryote evolution. We explore this challenge through experimental taphonomy of nuclei in a living eukaryote and microscale physical and chemical characterization of putative nuclei in embryo-like fossils from the early Ediacaran Weng'an Biota. The fossil nuclei exhibit diverse preservational modes that differ in shape, presence or absence of an inner body and the chemistry of the associated mineralization. The nuclei are not directly fossilized; rather, they manifest as external moulds. Experimental taphonomy of epidermal cells from the common onion (Allium cepa) demonstrates that nuclei are more decay resistant than their host cells, generally maintaining their physical dimensions for weeks to months post-mortem, though under some experimental conditions they exhibit shrinkage and/or become shrouded in microbial biofilms. The fossil and experimental evidence may be rationalized in a single taphonomic pathway of selective mineralization of the cell cytoplasm, preserving an external mould of the nucleus that is itself resistant to both decay and mineral replication. Combined, our results provide both a secure identification of the Weng'an nuclei as well as the potential of a fossil record of organelles that might help arbitrate in long-standing debates over the relative and absolute timing of the evolutionary assembly of eukaryote-grade cells.

鉴定化石细胞器的挑战长期以来阻碍了解释早期真核生物进化过程中化石记录的尝试。我们通过活的真核生物中的核实验拓扑学和来自早期Ediacaran Weng'an Biota的胚胎样化石中推定核的微观物理和化学表征，探索了这一挑战。化石核展现出多种保存方式，这些保存方式的形状，内部主体的存在与否以及相关矿化的化学性质都不同。原子核不直接被化石。相反，它们表现为外部霉菌。从共用洋葱表皮细胞的实验埋藏（洋葱）表明核比它们的宿主细胞更具抗腐性，通常在死后数周至数月内仍保持其物理尺寸，尽管在某些实验条件下它们显示出收缩和/或被微生物生物膜覆盖。化石和实验证据可以在细胞质选择性矿化的一条单一的染色体学途径中进行合理化，从而保留了自身对衰变和矿物质复制均具有抵抗力的细胞核外部霉菌。结合起来，我们的结果既可提供对ng安核的可靠鉴定，又可提供细胞器化石记录的潜力，这可能有助于在有关真核生物级细胞进化组装的相对和绝对时机的长期辩论中进行仲裁。