The shell-less, worm-shaped Caudofoveata (=Chaetodermomorpha) is one of the least known groups of molluscs. The taxon consists of 141 recognized species found from intertidal environments to the deep-sea where they live burrowing in sediment. Evolutionary relationships of the group have been debated, but few studies based on morphological or molecular data have investigated the phylogeny of the group. Here we use molecular phylogenetics to resolve relationships among and within families of Caudofoveata. Phylogenetic analyses were performed using selected mitochondrial and nuclear genes from species from all recognized families of Caudofoveata. In resulting trees and contrary to traditional views, Prochaetodermatidae forms the sister clade to a clade containing the other two currently recognized families, Chaetodermatidae and Limifossoridae. The monophyly of Prochaetodermatidae is highly supported, but Limifossoridae and Chaetodermatidae are not recovered as monophyletic. Most of the caudofoveate genera are also not recovered as monophyletic in our analyses. Thus results from our molecular data suggest that the current classification of Caudofoveata is in need of revision, and indicate evolutionary scenarios that differ from previously proposed hypotheses based on morphology.

无壳，蠕虫状的Caudofoveata（= Chaetodermomorpha）是最鲜为人知的软体动物群之一。该分类单元包括从潮间带环境到深海的141种公认物种，它们生活在底泥中。该组的进化关系一直存在争议，但是基于形态学或分子数据的研究很少研究该组的系统发育。在这里，我们使用分子系统发育学来解决Caudofoveata家族之间及其内部的关系。系统发育分析是使用线粒体和核基因从来自所有公认的Caudofoveata家族的物种中进行的。在产生的树木中，与传统观点相反，Prochaetodermatidae将姐妹进化枝形成包含另外两个当前公认的科（Chaetodermatidae和Limifossoridae）的进化枝。甲壳纲的单亲科受到高度支持，但Limifossoridae和Chaetodermatidae不能作为单系的而被回收。在我们的分析中，大多数caudofoveate属也未恢复为单系的。因此，从我们的分子数据得出的结果表明，目前需要对孔洞藻的分类进行修订，并指出与基于形态学的先前提出的假设不同的进化方案。