Liliatrema is a small genus of trematodes consisting of two species. Its systematic position has long been debated, partly because of the confusing reports about the structure of male terminal genitalia. Here we test the phylogenetic position of the genus Liliatrema using data on complete 18S rRNA and partial 28S rRNA gene sequences obtained for Liliatrema skrjabini. We also provide a detailed description of terminal genitalia in adult specimens of L. sobolevi and metacercariae of both Liliatrema species. The results of the 28S rDNA-based phylogenetic analysis indicate that Liliatrema falls within a well-supported clade, which also includes Apophallus and traditional opisthorchiids. This clade, in turn, is nested within a well-supported clade, containing Euryhelmis, Cryptocotyle and Scaphanocephalus. In the 18S+8S rDNA analysis, Liliatrema appears as a sister-taxon to the Cryptocotyle + Euryhelmis group. The Liliatrema + (Cryptocotyle + Euryhelmis) clade is a well-supported sister-group to the traditional opisthorchiids. The morphology of the terminal genitalia of the liliatrematids also corresponds to that of the opisthorchioids. Thus, the results of our morphological and phylogenetic analyses favour an unexpected conclusion that the genus Liliatrema belongs to the Opisthorchioidea. We propose that the genera Liliatrema, Apophallus, Euryhelmis, Cryptocotyle and Scaphanocephalus belong, respectively, within the subfamilies Liliatrematinae, Apophallinae, Euryhelminthinae and Cryptocotylinae of the family Opisthorchiidae.

中文翻译：

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Liliatrema属的阿片类足动物概念（Trematoda：Plagiorchiida：Opisthorchioidea）：意想不到的系统位置

lialiatrema是由两个物种组成的小吸虫属。它的系统地位长期以来一直受到争论，部分原因是关于男性末梢生殖器结构的报告令人困惑。在这里，我们使用关于Liliatrema skrjabini获得的完整18S rRNA和部分28S rRNA基因序列的数据来测试Liliatrema属的系统发生位置。我们还提供了对两个Liliatrema物种的L. sobolevi和metacercariae的成年标本中的末梢生殖器的详细描述。基于28S rDNA的系统发育分析结果表明，Liliatrema属于良好支持的进化枝，其中也包括Apophallus和传统的阿片类药物。反过来，该进化枝嵌套在一个支撑良好的进化枝中，该进化枝包含Euryhelmis，Cryptocotyle和Scaphanocephalus。在18S + 8S rDNA分析中，Liliatrema似乎是Cryptocotyle + Euryhelmis组的姐妹分类单元。所述Liliatrema +（Cryptocotyle + Euryhelmis）进化枝是一个很好的支持姐妹组传统的opisthorchiids。lia虫的末端生殖器的形态也与阿片类鸦片类动物的形态相对应。因此，我们的形态学和系统发育分析结果支持出人意料的结论，即百合科（Liliatrema）属于Opisthorchioidea。我们建议，属Liliatrema，Apophallus，Euryhelmis，Cryptocotyle和Scaphanocephalus属，分别亚科Liliatrematinae，Apophallinae，Euryhelminthinae和家庭Opisthorchiidae的Cryptocotylinae内。