Data from: Three-dimensional preservation of cellular and subcellular structures reveal 1.6 billion-year-old probable crown-group red algae

The ~1.6 Ga Tirohan Dolomite of the Lower Vindhyan in central India contains phosphatized stromatolitic microbialites. We report from there uniquely well-preserved fossils interpreted as crown-group rhodophytes (red algae). The filamentous form Rafatazmia chitrakootensis n.gen, n.sp. has uniserial rows of large cells and grows through diffusely distributed septation. Each cell has a centrally suspended, conspicuous rhomboidal disk interpreted as a pyrenoid. The septa between the cells have central structures that may represent pit connections and pit plugs. Another filamentous form, Denaricion mendax n.gen., n.sp., has coin-like cells reminiscent of those in large sulfur-oxidizing bacteria, but much more recalcitrant than the liquid-vacuole-filled cells of the latter. Its wider affinities are uncertain. Ramathallus lobatus n.gen., n.sp. is a lobate sessile alga with pseudoparenchymatous thallus and apparent tetraspore formation, suggesting florideophycean affinity. Rafatazmia and Ramathallus are interpreted as crown-group multicellular rhodophytes, antedating the oldest previously accepted red alga in the fossil record by about 400 million years.

印度中部温德亚群下部（Lower Vindhyan）时代约1.6 Ga（16亿年）的蒂罗汉白云岩（Tirohan Dolomite）中，赋存磷酸盐化叠层石微生物岩（stromatolitic microbialites）。本研究在此地层中报道了一批保存状态极为完好的化石，其被解释为冠群红藻（crown-group rhodophytes）。其中丝状形态类群查特卡尔拉夫塔齐藻（Rafatazmia chitrakootensis n.gen, n.sp.）具有单列大型细胞列，通过弥散分布的细胞分隔完成生长；每个细胞均带有一个中央悬挂的显著菱形盘结构，该结构被解释为淀粉核（pyrenoid）；细胞间的隔膜带有中央结构，推测其对应纹孔连接（pit connections）与纹孔塞（pit plugs）。
另一类丝状形态类群门达西纳里西藻（Denaricion mendax n.gen., n.sp.）具有类似大型硫氧化细菌的硬币状细胞，但其抗分解能力远强于后者充满液泡的细胞，其更广泛的分类学亲缘关系尚不明确。
叶状拉马塔藻（Ramathallus lobatus n.gen., n.sp.）为叶状固着藻类，拥有假薄壁组织叶状体，且存在疑似四分孢子形成的结构，提示其具有红藻纲（Florideophyceae）亲缘关系。
研究认为拉夫塔齐藻与拉马塔藻均属于冠群多细胞红藻，其出现时间较此前化石记录中公认的最古老红藻早约4亿年。