ABSTRACT. – Scolelepis neglecta Surugiu, 2016 is a polychaete species that was described from the Cantabrian coast of Asturias (northern Spain) based only on anterior fragments from museum collections. Recently collected live material of S. neglecta from the intertidal muddy sand flats of the Villaviciosa estuary (Asturias, Bay of Biscay, northern Spain), has enabled us to report some new, previously unknown morphological characters, such as the shape of the pygidium, the shape, number and distribution of the notopodial hooded hooks, and to assess the validity of S. neglecta by the means of molecular analyses. In order to reveal the taxonomic relationships between S. squamata from the Black Sea, S. neglecta from northern Spain and other species of Scolelepis, we have compared sequences of the mitochondrial cytochrome oxidase subunit 1 (COI) gene obtained in the present study with those available in GenBank or in BOLD Systems databases. Molecular phylogeny reconstruction revealed a clear separation of S. neglecta as a stand-alone clade. The molecular analysis also indicated that in the Black Sea exist two genetically distinct species of Scolelepis, both previously referred to as S. squamata, but none of them identical to S. squamata whose sequences exist in GenBank. These species are herein designated as Scolelepis cf. cirratulus and Scolelepis cf. mesnili, respectively, until new material for both species, especially from the type localities, will be available for molecular studies. The lowest genetic distance values were found between S. neglecta

and Scolelepis

cf.

cirratulus

from the Black Sea and the highest ones were found between S. neglecta and

S. goodbodyi

from Brazil and S. squamata from the west coast of North America. Apart from

providing COI sequences for S. neglecta and for two species of Scolelepis from the Black Sea,

this is the first study which attempts to provide inferences about the phylogenetic relationships

between species belonging to the genus Scolelepis.