BACKGROUND AND AIMS Structurally preserved arbuscular mycorrhizas from the Lower Devonian Rhynie chert represent core fossil evidence of the evolutionary history of mycorrhizal systems. Moreover, Rhynie chert fossils of glomeromycotan propagules suggest that this lineage of arbuscular fungi was morphologically diverse by the Early Devonian; however, only a small fraction of this diversity has been formally described and critically evaluated. METHODS Thin sections, previously prepared by grinding wafers of chert from the Rhynie beds, were studied by transmitted light microscopy. Fossils corresponding to the description of Archaeospora spp. occurred in 29 slides, and were measured, photographed, and compared to modern-day species in that genus. KEY RESULTS Sessile propagules <85 µm in diameter, some still attached to a sporiferous saccule, were found in early land plant axes and the chert matrix; they developed, in a similar manner to extant Archaeospora, laterally or centrally within the saccule neck. Microscopic examination and comparison with extant fungi showed that, morphologically, the fossils share the characters used to circumscribe the genus Archaeospora (Glomeromycota; Archaeosporales; Archaeosporaceae). CONCLUSIONS The fossils can be assigned with confidence to the extant family Archaeosporaceae, but because molecular analysis is necessary to place organisms in these taxa to present-day genera and species, they are placed in a newly proposed fossil taxon, Archaeosporites rhyniensis.

中文翻译：

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Archaeosporites rhyniensis gen。等 sp. 十一月 (Glomeromycota, Archaeosporaceae) 来自下泥盆纪 Rhynie 燧石：4 亿多年形态学未发生变化的真菌谱系

背景和目的 来自下泥盆统 Rhynie 燧石的结构上保存的丛枝菌根代表了菌根系统进化史的核心化石证据。此外，球藻繁殖体的 Rhynie chert 化石表明，这种丛枝真菌谱系在早泥盆世具有形态多样性；然而，这种多样性中只有一小部分得到了正式描述和批判性评估。方法 用透射光显微镜研究先前通过研磨来自 Rhynie 床的燧石晶片制备的薄片。对应于 Archaeospora spp 描述的化石。发生在 29 张幻灯片中，并被测量、拍照并与该属的现代物种进行比较。主要结果 无柄繁殖体直径 <85 µm，一些仍附着在孢子囊上，在早期陆地植物轴和燧石矩阵中发现；它们以与现存古孢子相似的方式在球囊颈内横向或中央发育。显微镜检查和与现存真菌的比较表明，在形态学上，这些化石具有用于界定古孢菌属（Glomeromycota；Archaeosporales；Archaeosporaceae）的特征。结论 这些化石可以自信地归于现存的古孢子科，但由于分子分析对于将这些分类群中的生物体定位到当今的属和种是必要的，因此将它们放置在新提出的化石分类群 Archaeosporites rhyniensis 中。显微镜检查和与现存真菌的比较表明，在形态学上，这些化石具有用于界定古孢菌属（Glomeromycota；Archaeosporales；Archaeosporaceae）的特征。结论 这些化石可以自信地归于现存的古孢子科，但由于分子分析对于将这些分类群中的生物体定位到当今的属和种是必要的，因此将它们放置在新提出的化石分类群 Archaeosporites rhyniensis 中。显微镜检查和与现存真菌的比较表明，在形态学上，这些化石具有用于界定古孢菌属（Glomeromycota；Archaeosporales；Archaeosporaceae）的特征。结论 这些化石可以自信地归于现存的古孢子科，但由于分子分析对于将这些分类群中的生物体定位到当今的属和种是必要的，因此将它们放置在新提出的化石分类群 Archaeosporites rhyniensis 中。