创建Triadium以包括Triadiumcaudatum。Further,包括其他四个物种,T、最小值,T.galea,T.elongatum,还有T.Magnum,都共享一个独特的头盔形身体。Wolska和Grain认为,将T.minimum和T.galea纳入Triadinium是基于表面形态方面进行的,并建立了两个新属来适应这些物种:Circodinium和Gassovskiella。尽管多个作者已经研究了Entodiniomorphida内部的系统发育关系,他们都没有讨论头盔形的内齿线虫的进化关系。我们进行了分子系统发育,并重新审视了旧文献,以挖掘形态学数据来解释我们的结果。根据我们的分析,头盔状的身体是同质的,可能是从至少三个不同的内齿线虫祖先进化而来的。Circodinium最小值与Blepharocorythidae的成员有关,T.caudatum出现在Spirodiniidae中,G.galea出现在Polydiniellidae中。这种系统发育假设部分得到了C.minimum和T.caudatum的不应构造和超微结构信息的支持。然而,这种形态信息对于polydinielids是不可用的。为了揭示头盔状纤毛虫的进化,未来的工作应集中于收集有关肉芽胞杆菌和其他Triadinium物种的脆弱性和超微结构的信息。
Triadinium was created to include Triadinium caudatum. Further, four other species were included, T. minimum, T. galea, T. elongatum, and T. magnum, all sharing a characteristic helmet-shaped body. Wolska and Grain argued that the inclusion of T. minimum and T. galea into Triadinium was done based on superficial morphological aspects, and established two new genera to accommodate these species: Circodinium and Gassovskiella. Although the phylogenetic relationships within Entodiniomorphida have been investigated by multiple authors, none of them discussed the evolutionary relationship of helmet-shaped entodiniomorphids. We performed molecular phylogenetics and revisited old literature digging for morphological data to explain our results. According to our analyses, the helmet-shaped body is homoplastic and may have evolved from at least three different entodiniomorphid ancestors. Circodinium minimum is phylogenetically related to members of Blepharocorythidae, T. caudatum emerged within Spirodiniidae and G. galea within Polydiniellidae. This phylogenetic hypothesis is partially supported by information on infraciliature and ultrastructure of C. minimum and T. caudatum. However, such morphological information is not available for polydiniellids. In order to shed some light into the evolution of the helmet-shaped ciliates, future works should focus to collect information on the infraciliature and the ultrastructure of Polydiniella mysorea and of other Triadinium species.