Systematic re-structure and new species of Sphaerodoridae (Annelida) after morphological revision and molecular phylogenetic analyses of the North East Atlantic fauna

Detailed morphological study of more than 2600 North East Atlantic (NEA) sphaerodorids (Sphaerodoridae, Annelida) and phylogenetic analyses of DNA sequences of representatives of several identified morphospecies enforced changing the current systematic classification within the family, allowed the discovery of new species, provided new information about the morphological and genetic characterisation of members of this group, and increased the species occurrence data to better infer their geographic and bathymetric distribution ranges. Phylogenetic analyses of nuclear (18S rRNA and 28S rRNA) and mitochondria) sequences (COI and 16S rRNA) of NEA short-bodied sphaerodorids revealed outstanding results including paraphyly of the genera Sphaerodoropsis, Sphaerodoridium, and Sphaerephesia. The number of longitudinal and transverse rows of dorsal macrotubercles is proposed as potential synapomorphies for the main clades, and are consequently herein used for the genera delimitation. The new classification proposed here implies nomenclatural changes and the erection of a new genus, Geminofilum gen. n., to accommodate the species previously considered as Sphaerodoropsis with two transverse rows of dorsal macrotubercles per segment. Four species arc being described herein: Euritmia nordica Capa & Bakken, sp. n., Sphaerephesia multichaeta Capa, Moreira & Parapar, sp. n., Sphaerephesia ponsi Capa, Parapar & Moreira, sp. n., and Sphaerodoridium celiae Moreira, Capa & Parapar, sp. n. Characterisation of the other 21 species, including updated iconography, and an identification key to all NEA short-bodied sphaerodorids arc provided.