Description of Euchone anceps sp. nov. (Annelida: Sabellidae) from the Mediterranean Sea and Northeast Atlantic, with remarks on the difficulty of generic definition

The problem of the generic placement of some peculiar Mediterranean and Atlantic sabellids, showing a mixture of features found in the genera Euchone and Paradialychone, is addressed. Due to the high similarity to E. pseudolimnicola, this peculiar taxon had previously been informally named Euchone cfr. pseudolimnicola. However, while the presence of a simple pre-pygidial depression without lateral wings or a distinct ridge in the uppermost margin is similar to Dialychone and Paradialychone, the dentition of thoracic and abdominal uncini resembles that found in Paradialychone. In this study, the morphological features of Mediterranean and British material were re-examined and compared to E. pseudolimnicola specimens, and a cladistics analysis was performed. The genus Euchone appears not well defined; E. cfr. pseudolimnicola and E. pseudolimnicola are located close to each other and also located in the area of the phylogenetic tree containing the other examined Euchone species. We suggest to maintain both these taxa within the genus Euchone until a revision based on the examination of type material of all the Euchone species is performed. The new species Euchone anceps sp. nov. has been described, and the large morphological variability existing in some Mediterranean material is also addressed. An updated taxonomic key for the species of the considered genera present in Northeast Atlantic and Mediterranean Sea is also provided.