Myzostomida comprise a group of marine worms associated mainly with echinoderms since the Carboniferous. Due to their unusual morphology the phylogenetic position in relation to other Lophotrochozoa is discussed since their description. According to different morphological and molecular markers the Myzostomida are either close to Platyzoa or Annelida. Here we investigated small non-coding RNAs of Myzostoma cirriferum to infer the phylogenetic position of myzostomids. Based on transcriptomic data collected by Illumina Deep Sequencing we analyzed the microRNA (miRNA) families occurring in M. cirriferum. Phylogenetic analysis revealed the presence of 13 miRNA-families exclusively shared by Annelida (including Sipuncula) and Myzostomida, as such highly significantly supporting an annelid origin of myzostomids. Furthermore, using a mapping-approach and secondary structure models we predicted several miRNA-candidates unique for myzostomids.

中文翻译：

---

小RNA的深度测序证实了Myzostomida的无亲和力。

自石炭纪以来，Myzostomida包括一组主要与棘皮动物相关的海洋蠕虫。由于它们不寻常的形态，自描述以来就讨论了相对于其他杆毛虫的系统发育位置。根据不同的形态学和分子标记，Myzostomida接近于Platyzoa或Annelida。在这里，我们调查了小型的Myzostoma cirriferum的非编码RNA，以推断mystostomids的系统发生位置。基于Illumina Deep Sequencing收集的转录组数据，我们分析了发生在柑桔分枝杆菌中的microRNA（miRNA）家族。系统发育分析表明，存在13个miRNA家族，仅由Annelida（包括Sipuncula）和Myzostomida共享，因为它们高度显着地支持了Mystostomids的无脊椎动物起源。此外，