A New Heteronemertean Genus with Variable Potential of Anterior Regeneration for Species Formerly Belonging to (Nemertea: Pilidiophora).

The heteronemertean genus Sowerby, 1805, currently accommodating about 100 species, is known to be non-monophyletic and is in a desperate need of taxonomic revision. In this article, we focus on a group of species including Takakura, 1898, (Hubrecht, 1879) auct., Coe, 1904, and Takakura, 1898. These four morphologically similar species formed a clade to the exclusion of the type species, (Gunnerus, 1770), on a molecular phylogeny based on partial sequences of the 16S rRNA, 18S rRNA, 28S rRNA, cytochrome oxidase subunit I, and histone H3 genes. For this clade we propose the name gen. nov. We redescribe auct. from Japan as sp. nov. clade was nested within a larger clade that also contained members of Chernyshev, Polyakova, Turanov, and Kajihara, 2017, Gibson, 1990, Renier in Meneghini, 1847, and Riser, 1993. We observed that body fragments from the intestinal region regenerated a head in comb. nov. and comb. nov., but did not in sp. nov. The type specimen of Takakura, 1898 was most likely a regenerating individual of comb. nov. We synonymize with , giving nomenclatural priority to the latter. In addition, Coe, 1934 is herein also synonymized with . We speculate that the unusually wide geographic distribution of comb. nov. is related to its ability to regenerate head from fragments of body.