When a genus must become two: resurrection of Pelagella Gray, 1850 with the description of six new species

Goniodoris is the third most diverse genus of the nudibranch family Goniodorididae. The genus has undergone several taxonomic changes, with c. one-third of the recognized species of Goniodoris having been synonymized (most of these are junior synonyms of genera from other families). In addition, Goniodoris includes other synonymized genera within it, such as Pelagella, which was erected for Doris pareti. This species was synonymized with Goniodoris castanea and the genus Pelagella went almost unnoticed. In the present study, we investigate the systematics of the genus Goniodoris by examining specimens of G. castanea from England and Spain, G. joubini from Hawaii and six undescribed Goniodoris species from Australia, the Philippines and Mozambique. The morphology of the new species is studied using dissections of the internal organs and scanning electron micrographs of the radulae, labial cuticles and the penis. We also carried out phylogenetic analyses using partial DNA sequences of mitochondrial and nuclear genes. These analyses show that the type species of Goniodoris, G. nodosa, is not a member of the clade constituted by the focal species of our study; the valid name for this clade is Pelagella. Six new species of Pelagella, P. albopunctata n. sp., P. balanoyensis n. sp., P. longicornis n. sp., P. scottjohnsoni n. sp., P. rubrobranchiata n. sp. and P. vitrea n. sp., are described.