Although biomineralized skeletal elements dominate the Phanerozoic fossil record, they did not become common until ~550–520 Ma when independent acquisitions of biomineralization appeared in multiple lineages of animals and a few protists (single-celled eukaryotes). Evidence of biomineralization preceding the late Ediacaran is spotty aside from the apatitic scale microfossils of the ~811 Ma Fifteenmile Group, northwestern Canada. Here, we describe scale-shaped microfossils from four vase-shaped microfossil (VSM)-bearing units of later Tonian age: the Togari Group of Tasmania, Chuar and Pahrump groups of southwestern United States, and the Roaldtoppen Group of Svalbard. These scale-shaped microfossils consist of thin, ~13 micron-long plates typically surrounded by a 1–3 micron-thick colorless envelope; they are found singly and in heterotypic and monotypic clusters of a few to >20 specimens. Raman spectroscopy and confocal laser scanning microscopy indicate these microfossils are composed of apatite and kerogen, just as is seen in the Fifteenmile Group scale microfossils. Despite compositional similarity, however, these scales are probably not homologous, representing instead, an independent acquisition of apatite mineralization. We propose that these apatite-kerogen scale-shaped microfossils are skeletal elements of a protistan cell. In particular, their consistent co-occurrence with VSMs, and similarities with scales of arcellinid testate amoebae, a group to which the VSMs are thought to belong, suggest the possibility that these microfossils may be test-forming scales of ancient arcellinid testate amoebae. The apparent apatite biomineralization in both these microfossils and the Fifteenmile scales is unexpected given its exceedingly rare use in skeletons of modern protists. This modern absence is attributed to the extravagance of using a limiting nutrient in a structural element, but multiple occurrences of apatite biomineralization in the Tonian suggest that phosphorus was not a limiting nutrient for these organisms, a suggestion consistent with the idea that dissolved seawater phosphate concentrations may have been higher at this time.

中文翻译：

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来自死亡谷、大峡谷、塔斯马尼亚和斯瓦尔巴群岛的花瓶形微化石组合中的磷酸盐鳞片

尽管生物矿化骨骼元素在显生宙化石记录中占主导地位，但直到约 550-520 Ma 时，生物矿化的独立获得出现在多个动物谱系和一些原生生物（单细胞真核生物）中时，它们才变得普遍。除了加拿大西北部~811 Ma Fifteenmile Group 的磷灰石尺度微化石外，埃迪卡拉纪晚期之前的生物矿化证据是参差不齐的。在这里，我们描述了来自托尼亚时代晚期的四个花瓶形微化石 (VSM) 单元的鳞片状微化石：塔斯马尼亚的托加里群、美国西南部的 Chuar 和 Pahrump 群，以及斯瓦尔巴群岛的 Roaldtoppen 群。这些鳞片状微化石由约 13 微米长的薄板组成，通常被 1-3 微米厚的无色外壳包围；它们被单独发现，并且在少数至 >20 个标本的异型和单型集群中被发现。拉曼光谱和共聚焦激光扫描显微镜表明这些微化石由磷灰石和干酪根组成，正如在 Fifteenmile Group 规模的微化石中所见。然而，尽管成分相似，但这些尺度可能不是同源的，而是代表磷灰石矿化的独立获得。我们认为这些磷灰石-干酪根鳞片状微化石是原生生物细胞的骨骼元素。特别是，它们与 VSM 的一致共存，以及与被认为属于 VSM 的组arcellinid 遗嘱变形虫的尺度相似，表明这些微化石可能是古代arcellinid 遗嘱变形虫的测试形成尺度的可能性。鉴于磷灰石在现代原生生物骨骼中的用途极为罕见，因此这些微化石和十五英里尺度中明显的磷灰石生物矿化是出乎意料的。这种现代的缺失归因于在结构元素中使用限制性营养素的过度使用，但托尼亚人多次发生磷灰石生物矿化表明磷不是这些生物的限制性营养素，这一建议与溶解海水磷酸盐浓度的观点一致此时可能更高。