The systematics of Hypotricha is one of the most puzzling problems in ciliate biology, having spanned numerous conflicting hypotheses with unstable relationships at various levels in molecular trees, for which the constant addition of newly discovered species has only increased the confusion. The hypotrichs comprise a remarkable morphologically diversified group of ciliates, and the phylogenetic potential of morphological traits is generally recognized. However, such characters were rarely used in phylogenetic reconstructions, and congruence with molecular data never assessed from simultaneous analyses. To properly reconciliate morphological and molecular information, maximum-likelihood and parsimony analyses of 79 morphological characters and 18S rDNA sequences were performed for 130 ingroup terminals, broadly sampled to represent the known hypotrich diversity. As result, well-supported and relatively stable clades were recovered, based on which the redefined Hypotricha comprises at least six higher taxa: The “arcuseriids”, Holostichida, Parabirojimida, and the “amphisiellids”, plus the two large clades Kentrurostylida nov. tax. (Hispidotergida nov. tax. and Simplicitergida nov. tax.) and Diatirostomata nov. tax. (“bistichellids”, “kahliellids”, Gonostomatida and Dorsomarginalia [Postoralida nov. tax. and Uroleptida]). Each taxon was circumscribed by synapomorphies, of which most were homoplastic, as the natural history of hypotrichs is portrayed by an outstanding quantity of convergences and reversions.

Hypotricha 的系统学是纤毛虫生物学中最令人费解的问题之一，它跨越了许多相互矛盾的假设，在分子树的各个层次上都有不稳定的关系，而新发现的物种的不断增加只会增加混乱。短毛虫包括一个显着的形态多样化的纤毛虫群，形态特征的系统发育潜力得到普遍认可。然而，这些特征很少用于系统发育重建，并且从未通过同步分析评估与分子数据的一致性。为了正确协调形态学和分子信息，对 130 个组内终端进行了 79 个形态特征和 18S rDNA 序列的最大似然和简约分析，广泛采样以代表已知的hypotrich多样性。结果，得到了良好支持和相对稳定的进化枝，在此基础上重新定义的 Hypotricha 包括至少六个更高的分类群：“arcuseriids”、Holostichida、Parabirojimida 和“amphisiellids”，加上两个大进化枝 Kentrurostylida nov。税。（Hispidotergida nov. tax. 和 Simplicitergida nov. tax.）和 Diatirostomata nov. 税。（“bistichellids”、“kahliellids”、Gonostomatida 和 Dorsomarginalia [Postoralida nov. tax. and Uroleptida]）。每个分类群都受到突触的限制，其中大多数是同质的，因为hypotrichs的自然历史被大量的收敛和逆转所描绘。基于此，重新定义的 Hypotricha 包括至少六个更高的分类群：“arcuseriids”、Holostichida、Parabirojimida 和“amphisiellids”，加上两个大的进化枝 Kentrurostylida nov。税。（Hispidotergida nov. tax. 和 Simplicitergida nov. tax.）和 Diatirostomata nov. 税。（“bistichellids”、“kahliellids”、Gonostomatida 和 Dorsomarginalia [Postoralida nov. tax. and Uroleptida]）。每个分类群都受到突触的限制，其中大多数是同质的，因为hypotrichs的自然历史被大量的收敛和逆转所描绘。基于此，重新定义的 Hypotricha 包括至少六个更高的分类群：“arcuseriids”、Holostichida、Parabirojimida 和“amphisiellids”，加上两个大的进化枝 Kentrurostylida nov。税。（Hispidotergida nov. tax. 和 Simplicitergida nov. tax.）和 Diatirostomata nov. 税。（“bistichellids”、“kahliellids”、Gonostomatida 和 Dorsomarginalia [Postoralida nov. tax. and Uroleptida]）。每个分类群都受到突触的限制，其中大多数是同质的，因为hypotrichs的自然历史被大量的收敛和逆转所描绘。Gonostomatida 和 Dorsomarginalia [Postoralida nov. 税。和尿肽]）。每个分类群都受到突触的限制，其中大多数是同质的，因为hypotrichs的自然历史被大量的收敛和逆转所描绘。Gonostomatida 和 Dorsomarginalia [Postoralida nov. 税。和尿肽]）。每个分类群都受到突触的限制，其中大多数是同质的，因为hypotrichs的自然历史被大量的收敛和逆转所描绘。