In the biogeographical and taxonomical literature before the 1980s there was a wide perception that widespread, often referred to as ‘cosmopolitan’, species were very common among polychaetes. Here we discuss the origins of this perception, how it became challenged, and our current understanding of marine annelid distributions today. We comment on the presence of widely distributed species in the deep sea and on artificially extended ranges of invasive species that have been dispersed by anthropogenic means. We also suggest the measures needed to revolve the status of species with reported cosmopolitan distributions and stress the value of museum collections and vouchers to be associated with DNA sequences in resolving species distributions.

Terebelliformia comprises a large group of sedentary polychaetes which live from the intertidal to the deep sea. The majority live in tubes and are selective deposit feeders. This study synthesises the current knowledge of this group, including their distribution, in the different biogeographic regions. We highlight the new methodologies being used to describe them and the resolution of species complexes occurring in the group. The main aim of this review is to highlight the knowledge gaps and to stimulate research in those directions, which will allow for knowledge of their distribution and abundances to be used by ecologists and managers.

This work is the last of four papers of the Spaghetti Project, aiming to revise the species of terebellids, a.k.a. “spaghetti” worms, present in the European French waters. In this last paper the Terebellidae, sensu stricto, from French waters are revised based, on material available in the French marine stations, type materials stored in the MNHN collection and newly collected specimens. Nine new species are described using both morphological and molecular tools: Eupolymnia gili n. sp., E. lacazei n. sp., E. meissnerae n. sp., Lanice kellyslateri n. sp., Paramphitrite dragovabeci n. sp., Pista labruneae n. sp., P. miosseci n. sp., P. sauriaui n. sp., and Terebella banksyi n. sp. European species of Eupolymnia are distinguished mainly by the shape of the lateral lobes and the size of the branchial stems. The two species belonging to Lanice genus are distinguished by the fusion of the first ventral shields, the shape of both noto- and neuropodia, and the pigmentation of the upper lip. The two species of Paramphitrite are distinguished by the presence or absence of a medial dorsal gap between the pairs of branchiae, by the shape of the lateral lobes and the presence or absence of a nephridial papilla on segment 4. The different species of Pista are distinguished by the number of pairs of branchiae, the shape of the lateral lobes and uncini. Finally, the two species of Terebella are distinguished by the number of segments with nephridial and genital papillae and the segments on which the branchiae occur. An identification key for European species of Terebellidae sensu stricto is also provided.

Taxonomy and distribution of Terebellides (Polychaeta: Trichobranchidae) in the northern South China Sea, with description of three new species

The large polychaete genus Polycirrus (Terebellida: Polycirridae) is revised based on a morphological study of the type material of most of the approximately 74 nominal species; 59 species, including a new species, P. coibensis n.sp., from the Pacific coast of Panama, are accepted as valid. All characters are reanalysed and discussed in the light of recent phylogenetic studies of terebellomorph taxa, and a standard set of characters is developed. Most of the 59 accepted species are redescribed and illustrations provided in order to facilitate future identifications of members of the genus. We designate a neotype for the type species of the genus, Polycirrus medusa Grube, 1850, and a lectotype for P. elisabethae McIntosh, 1915, in order to stabilize the concept and type locality of these taxa. A replacement name is proposed for Polycirrus kerguelensis McIntosh, 1885, which is a secondary junior homonym of Ereutho kergulenesis McIntosh, 1885, viz. Polycirrus macintoshi new name. Two species are newly synonymised: Polycirrus insignis Gravier, 1907 (senior synonym P. antarcticus (Willey, 1902)) and Polycirrus habitats Carrerette & Nogueira, 2013 (senior synonym, P. clavatus (Kinberg, 1867)). In addition, several previously synonymised species are reinstated. All available names in the genus are tabulated with type species and type localities and their taxonomic status is assessed. A key to all valid species is provided.