Ploeotids are an assemblage of rigid phagotrophic euglenids that have 10–12 pellicular strips and glide on their posterior flagellum. Molecular phylogenies place them as a poorly resolved, likely paraphyletic assemblage outside the Spirocuta clade of flexible euglenids, which includes the well-known phototrophs and primary osmotrophs. Here, we report SSU rRNA gene sequences from 38 ploeotids, using both single-cell and culture-based methods. Several contain group I or non-canonical introns. Our phylogenetic analyses place ploeotids in 8 distinct clades: Olkasia n. gen., Hemiolia n. gen., Liburna n. gen., Lentomonas, Decastava, Keelungia, Ploeotiidae, and Entosiphon. Ploeotia vitrea, the type of Ploeotia, is closely related to P. oblonga and Serpenomonas costata, but not to Lentomonas. Ploeotia cf. vitrea sensu Lax and Simpson 2013 is not related to P. vitrea and has a different pellicle strip architecture (as imaged by scanning electron microscopy): it instead represents a novel genus and species, Olkasia polycarbonata. We also describe new genera, Hemiolia and Liburna, for the morphospecies Anisonema trepidum and A. glaciale. A recent system proposing 13 suprafamilial taxa that include ploeotids is not supported by our phylogenies. The exact relationships between ploeotid groups remain unresolved and multigene phylogenetics or phylogenomics are needed to address this uncertainty.

蛇颈龙是刚性吞噬营养性的鳗鱼的组合，具有10–12个防护膜条并在其后鞭毛上滑动。分子系统发育将它们定位为柔韧的螺旋藻的螺旋藻进化枝之外的分辨率较差的，可能的寄生虫组合，其中包括众所周知的光养生物和原发同养生物。在这里，我们报告了使用单细胞和基于培养的方法从38个血小板减少的SSU rRNA基因序列。几个包含第I组或非规范内含子。我们的系统发育分析将拟蝇体置于8个不同的进化枝中：Olkasia n.。属，Hemiolia。gen。，Liburna n。gen。，Lentomonas，Decastava，Keelungia，Ploeotiidae和Entosiphon。Ploeotia vitrea（Ploeotia vitrea）是一种Ploeotia类型，与球形毕赤酵母（P. oblonga）和滨藜（Serpenomonas costata）有密切的关系，而与Lentomonas无关。Ploeotia比照 vitrea sensu Lax和Simpson 2013与P. vitrea无关，并且具有不同的防护膜条结构（通过扫描电子显微镜成像）：而是代表了一种新的属和种，即Olkasia polycarbonata。我们还描述了新属，Hemiolia和Liburna，为形态上的Anisonema trepidum和A. glaciale。我们的系统进化论不支持最近提出的建议的13种上皮类群，其中包括浮游动物类。血栓基团之间的确切关系仍未解决，需要多基因系统发育或系统基因组来解决这种不确定性。