The class Eustigmatophyceae includes mostly coccoid, freshwater algae, although some genera are common in terrestrial habitats and two are primarily marine. The formal classification of the class, developed decades ago, does not fit the diversity and phylogeny of the group as presently known and is in urgent need of revision. This study concerns a clade informally known as the Pseudellipsoidion group of the order Eustigmatales, which was initially known to comprise seven strains with oval to ellipsoidal cells, some bearing a stipe. We examined those strains as well as 10 new ones and obtained 18S rDNA and rbcL gene sequences. The results from phylogenetic analyses of the sequence data were integrated with morphological data of vegetative and motile cells. Monophyly of the Pseudellipsoidion group is supported in both 18S rDNA and rbcL trees. The group is formalized as the new family Neomonodaceae comprising, in addition to Pseudellipsoidion, three newly erected genera. By establishing Neomonodus gen. nov. (with type species Neomonodus ovalis comb. nov.), we finally resolve the intricate taxonomic history of a species originally described as Monodus ovalis and later moved to the genera Characiopsis and Pseudocharaciopsis. Characiopsiella gen. nov. (with the type species Characiopsiella minima comb. nov.) and Munda gen. nov. (with the type species Munda aquilonaris) are established to accommodate additional representatives of the polyphyletic genus Characiopsis. A morphological feature common to all examined Neomonodaceae is the absence of a pyrenoid in the chloroplasts, which discriminates them from other morphologically similar yet unrelated eustigmatophytes (including other Characiopsis‐like species).

中文翻译：

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走向现代分类的Eustigmatophytes，包括新单科植物的描述。十一月和三个新世代1。

Eustigmatophyceae 类主要包括球状、淡水藻类，尽管一些属在陆地生境中很常见，其中两个属主要是海洋。几十年前制定的该类别的正式分类不符合目前已知的该群体的多样性和系统发育，并且迫切需要修订。这项研究涉及一个非正式地称为Eustigmatales 目的Pseudellipsoidion组的进化枝，最初已知该进化枝包含七个具有椭圆形至椭圆形细胞的菌株，其中一些带有菌柄。我们检查了这些菌株以及 10 个新菌株，并获得了 18S rDNA 和rbc L 基因序列。将序列数据的系统发育分析结果与营养细胞和运动细胞的形态学数据相结合。单体的18S rDNA 和rbc L 树都支持Pseudellipsoidion组。该组被正式确定为新单胞菌科，除Pseudellipsoidion外，还包括三个新建立的属。通过建立Neomonodus gen。十一月 （与类型物种Neomonodus ovalis comb. nov.），我们最终解决了最初描述为Monodus ovalis并后来转移到Characiopsis和Pseudocharaciopsis属的物种的复杂分类历史。Characiopsiella gen. 十一月 （与类型物种Characiopsiella minima comb. nov.）和Munda将军 十一月 （与模式物种Munda aquilonaris）建立以容纳多系属Characiopsis的其他代表。所有检查过的新单胞菌科的一个共同的形态特征是叶绿体中没有类核蛋白，这将它们与其他形态相似但不相关的eustigmatophytes（包括其他Characiopsis样物种）区分开来。