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Sedentarian annelids are a diverse and heterogeneous group of marine worms representing more than 8600 species gathered in ca. 43 families. The attention brought to these organisms is unevenly distributed among these families, and the knowledge about them sometimes scarce. We review here the current knowledge about the families Acrocirridae, Cirratulidae (including Ctenodrilidae), Cossuridae, Longosomatidae, Paraonidae, and Sternaspidae in terms of biodiversity as well as the evolution of the taxonomy and systematics of each group. We present the challenges faced when studying these organisms and compare methodologies across groups and perspectives in future research.

We studied the innervation of unpaired branchial appendages using confocal laser scanning microscopy in two annelid species: Terebellides cf. stroemii (Trichobranchidae) and Cossura pygodactylata (Cossuridae). The branchial filament was found to be innervated by one unpaired segmental nerve coming from the ventral nerve cord at the level of chaetiger 2 in C. pygodactylata. This nerve lies transversally along the body wall and comes laterally to the base of the branchial filament. Such a structure indicates that (1) the branchial filament is unpaired and neither represents merged paired branchiae nor is related in its origin to prostomial appendages or peristomial ones, and (2) the branchial filament is the result of a shift of one of the paired segmental branchiae with parallel reduction of the second branchia in this pair. The branchial organ of T. cf. stroemii is innervated by paired segmental nerves from the first and second chaetigers. The segmental nerves are connected by longitudinal nerves going on the lateral sides of the body closer to the dorsum. One nerve on each side proceeds to the anterior part of the branchial stalk, and another nerve proceeds to the posterior part. All these nerves have transversal connections. The anterior stalk nerves come into the anterior branchial lobes, while the posterior nerves come to the posterior lobes. In the branchial lobes, the nerves give rise to thinner nerves, which go to each of the branchial lamellae. The present study confirms that the branchial organ of Terebellides has a paired nature and originates from segmental branchiae. Based on the number of innervating segmental nerves, we can conclude that the branchial organ of T. cf. stroemii is formed by two pairs of merged branchiae.

The anatomy of Cossura pygodactylata Jones, 1956 (Annelida; Cossuridae) is presented, based on the study of specimens collected during the BIOICE project in Icelandic waters and additional material from the White Sea. General gross external and internal anatomy were investigated by means of micro-computed tomography (micro-CT) and compared with results obtained with light microscopy histological sectioning (LMHS). Micro-CT revealed a highly regionalised gut, posterior to the pharyngeal cavity and oesophagus, divided in an anterior stomach and a posterior intestine with different morphologies. The stomach is in the thoracic region, dorsally positioned and divided in a short and narrow anterior part and a longer posterior one, with an increasing diameter towards its posterior end. Both stomach regions bear a dorsal infolding of tissue, along its inner wall, that resembles to the typhlosole of the Clitellata. The heart is dorsally located and contains a heart body above the hind stomach. The intestine is wider than the stomach, without dorsal infolding inside the lumen and filling most part of the internal body cavity. A transitional cup-shaped gut element connecting the stomach and the intestine could be observed at the level of the last thoracic segment. In general, the resolution of micro-CT images reflects reasonably well the main elements of gross external and internal anatomy of cossurids, and that of gut architecture in particular.

Two new species of Cossura Webster & Benedict, 1887 were found in material collected during sampling from the terminal lobes of the Congo deep-sea fan. They were described using light and scanning electron microscopy. Cossura platypus sp. nov. has 15–17 thoracic chaetigers, a prostomium longer than it is wide, with a widely rounded anterior margin, an abruptly expanded posterior prostomial ring the same length as the peristomium, without a mid-ventral notch, a branchial filament attached to the midlength of chaetiger 3, and a pygidium with three anal cirri. Cossura platypus sp. nov. is similar to C. brunnea Fauchald, 1972 but differs in the shape of the prostomium, which is widely rounded anteriorly in C. platypus sp. nov. and is broadly triangular in C. brunnea; furthermore, C. platypus sp. nov.is uniformly pale, whereas C. brunnea has dark pigmentation. Cossura candida Hartman, 1955 differs from C. platypus sp. nov. in the conical shape of the prostomium and 24–35 thoracic chaetigers. Cossura flabelligera sp. nov. has 16–19 thoracic chaetigers, a conical prostomium, and a branchial filament arising from the posterior part of chaetiger 2; the entire body, including the chaetae, is covered by a thick mucous sheath similar to the tunic of flabelligerids. Cossura flabelligera sp. nov. resembles C. longocirrata Webster & Benedict, 1887 in the position of the branchial filament, the shape of the prostomium, and the number of thoracic chaetigers; it differs in having a thick mucous sheath. This character seems to be unique for the Cossuridae.

The collection of Cossuridae at the Australian Museum was investigated. Nine species were identified. Most specimens were from New South Wales and Queensland, but some specimens were also from Victoria, New Zealand, Fiji, Borneo, and the Philippines. Three new species were described: Cossura hutchingsae n.sp., C. keablei n.sp., and C. queenslandensis n.sp. Cossura consimilis Read, 2000 was redescribed using non-type material. Cossura aciculata (Wu & Chen, 1977) was identified from the coast of Borneo and the Philippines for the first time, and intraspecific variability in the number of thoracic chaetigers noted for that species. Three species, C. cf. ginesi, C. cf. longocirrata and C. cf. pygodactylata, were found to be morphologically similar to C. ginesi, C. longocirrata, and C. pygodactylata, respectively, but probably represent new species as they were found far from the known areas of the listed species. A key of the known cossurid species of Australian and adjacent waters is given, and taxonomical characteristics of Cossuridae are discussed. ZhAdAn, AnnA. 2015. Cossuridae (Annelida: Polychaeta: Sedentaria) from Australian and adjacent waters: the first faunistic survey. Records of the Australian Museum 67(1): 1–24. Cossuridae Day, 1963 is a small family of benthic polychaetes. Cossuridae is composed of 23 species, all in the genus Cossura. Cossurids inhabit shallow marine sediments, and, in deep-sea habitats, they also commonly inhabit mixed sand and mud. In Australian waters, the family has been reported along the southern and eastern coasts, but specific species have not been previously identified (Hutchings & Murray, 1984; Hutchings, 2000). One species, Cossura consimilis Read, 2000, was identified in New Zealand. Cossuridae species are difficult to distinguish morph­ ologically and do not have many taxonomic characteristics. Some of the described species are very similar and differ by only one feature. For example, C. longocirrata Webster & Benedict, 1887 and C. pygodactylata Jones, 1956 differ by the presence of pygidial intercirral appendages in the latter, and C. soyeri Laubier, 1963 and C. consimilis differ by the positioning of the branchial filament. Some species have been described using incomplete specimens; the descriptions of those species are too short, and the most important characteristics of those species remain unknown (see Read, 2000, table 1 for review). Taxonomic revision of this family with reinvestigation of type materials and a large number of specimens for each species to reveal intraspecific variability and molecular genetic methods is required. The taxonomic characteristics used for the differentiation of cossurid species are as follows. Prostomium shape varies from conical (triangular from dorsal view) to round, trapezium-shaped and almost quadrangular. The length to width ratio of the prostomium is usually close to 1:1; refer to the discussion on the delineation of the prostomium and the peristomium below. The tip of the prostomium is never drawn and does not form a palpod as is the case in some

Genus Cossura Webster & Benedict, 1887 Cossura soyeri Laubier, 1963 DISTRIBUTION: NA, CA, SA. LITERATURE RECORDS: Cognetti-Varriale & Zunarelli-Vandini 1978; Vri��er 1979, 1984; Ambrogi et al. 1987; Požar-Domac 1994; Crema et al. 2001; Simonini et al. 2004; Maggiore & Keppel 2007; Ponti et al. 2007; Castelli et al. 2008. NEW RECORDS: BM 11, BM 21, BM 54, BM 55, BM 98., Published as part of Mikac, Barbara, 2015, A sea of worms: polychaete checklist of the Adriatic Sea, pp. 1-172 in Zootaxa 3943 (1) on page 29, DOI: 10.11646/zootaxa.3943.1.1, http://zenodo.org/record/244663, {"references":["Cognetti-Varriale, A. M. & Zunarelli-Vandini, R. (1978) Distribution des Polychetes sur les fonds meubles infralittoraux du Molise (Adriatique). Cahiers de Biologie Marine, 19, 37 - 45.","Vriser, B. (1979) Modifikacije meiofaune v umetno poluiranem lagunarnem ekosistemu. Bioloski Vestnik, 27 (1), 75 - 86.","Vriser, B. (1984) The structure and abundance of meiofauna in the inner parts of Piran, Strunjan and Koper bays (Gulf of Trieste, North Adriatic). Bioloski Vestnik, 32 (1), 121 - 136.","Ambrogi, R., Bedulli, D. & Fontana, P. (1987) Raccolta dei dati sul macrobenthos marino nella zona antistante la Centrale di Porto Tolle. Fase pre - operazionale (1979 - 1982). ENEL, Direzione Studi e Ricerche, Centro Ricerca Tecnica e Nucleare, Servizio Ambiente, 1 - 20.","Pozar-Domac, A. (1994) Index of the Adriatic Sea Polychaetes (Annelida, Polychaeta). Natura Croatica, 3, (Supplement 1), 1 - 23.","Crema, R., Prevedelli, D. & Castelli, A. (2001) Effect of submerged structures on the diversity of macrozoobenthos in the Northern Adriatic Sea. In: Faranda, F. M., Guglielmo, L. & Spezie, G. (Eds), Mediterranean Ecosystems: Structures and Processes. Springer - Verlag Italia, pp. 367 - 374. http: // dx. doi. org / 10.1007 / 978 - 88 - 470 - 2105 - 1 _ 48","Simonini, R., Ansaloni, I., Bonvicini Pagliai, A. M. & Prevedelli, D. (2004) Organic enrichment and structure of the macrozoobenthic community in the northern Adriatic sea in an area facing Adige and Po mouths. ICES Journal of marine Science, 61, 871 - 881. http: // dx. doi. org / 10.1016 / j. icesjms. 2004.06.018","Maggiore, F. & Keppel, E. (2007) Biodiversity and distribution of polychaetes and molluscs along the Dese estuary (Lagoon of Venice, Italy). Hydrobiologia, 588, 189 - 203. http: // dx. doi. org / 10.1007 / s 10750 - 007 - 0662 - 1","Ponti, M., Colangelo, M. A. & Ceccherelli, V. U. (2007) Composition, biomass and secondary production of the macrobenthic invertebrate assemblages in a coastal lagoon exploited for extensive aquaculture: Valle Smarlacca (northern Adriatic Sea). Estuarine, Coastal and Shelf Science, 75, 79 - 89. http: // dx. doi. org / 10.1016 / j. ecss. 2007.01.021","Castelli, A., Bianchi, C. N., Cantone, G., Cinar, M. E., Gambi, M. C., Giangrande, A., Iraci Sareri, D., Lanera, P., Licciano, M., Musco, L. & Sanfilippo, R. (2008) Annelida Polychaeta. In: Relini, G. (Ed), Checklist della flora e della fauna dei mari italiani (Parte I). Biologia Marina Mediterranea, 15 (Supplement 1), pp. 327 - 377."]}

Mikac, Barbara (2015): A sea of worms: polychaete checklist of the Adriatic Sea. Zootaxa 3943 (1): 1-172, DOI: http://dx.doi.org/10.11646/zootaxa.3943.1.1

Salazar-Vallejo, Sergio I., Carrera-Parra, Luis F., Muir, Alexander I., León-González, Jesús Angel De, Piotrowski, Christina, Sato, Masanori (2014): Polychaete species (Annelida) described from the Philippine and China Seas. Zootaxa 3842 (1): 1-68, DOI: http://dx.doi.org/10.11646/zootaxa.3842.1.1

Family Cossuridae Species: Cossura candida Hartman 1955 References: Souza (2008) Environment: Bay Depth: 1���4 m Coordinates: 27 �� 35 'S / 48 �� 35 'W, Published as part of Pagliosa, Paulo Roberto, Doria, Jo��o Gabriel, Alves, Giorgia Freitas, Almeida, Tito Cesar Marques De, Lorenzi, Luciano, Netto, Sergio Antonio & Lana, Paulo Da Cunha, 2012, Polychaetes from Santa Catarina State (southern Brazil): checklist and remarks on species distribution, pp. 1-49 in Zootaxa 3486 on page 14, DOI: 10.5281/zenodo.213667

This study summarizes taxonomic information on polychaetes from Santa Catarina State, southern Brazil, between25º57'S and 29º23'S, and provides species distribution records together with information on habitats, based on historicaldata and novel records from primary surveys. Rarefaction curves showed that most species were found in the shallowsublittoral (to 60 m) rather than in deep sublittoral (>60 m) or estuarine habitats. Altogether, 228 valid species belongingto 141 genera and 44 families were recorded. This inventory adds 141 new records to previous regional reports. We founda shift in occurrence of species when comparing data from the study area with data from both southward (29–33º S) andnorthward (23–26º S) sites. Few species were shared between consecutive sites: this could be a response to the regionalbehaviour of the atmosphere and water masses, with a progressive increase in the influence of subantarctic waters and a decrease in the influence of subtropical waters.

Cossura soyeri Laubier and Clymenella torquata (Leidy) are newly recorded for the Pacific Ocean. Praxillella praetermissa (Malmgren) is new to the northeast Pacific. Another species of Cossura (unidentifiable) and Maldanella harai (Izuka) are added to the fauna of Washington and British Columbia.Key words: Cossuridae, Maldanidae, new records, Northeast Pacific, Polychaetes

The family Cossuridae is monogeneric for Cossura Webster & Benedict, 1887 which currently has 28 known species, three of which already recorded for Brazilian coast. In the present study we describe Cossura yacy sp. nov. increasing to 29 the number of known Cossuridae species. We have found and analyzed 60 individuals of C. yacy sp. nov. from São Marcos estuarine complex (ca. 02°S; 44°W) around São Luís Harbor (Maranhão, Brazil). It differs from other species of genus also by the presence of the two pairs of nuchal organs at lateral margins of the peristomium, branchial filament in the median region of the third chaetiger and by short and long capillary smooth chaetae with spinulosa on the distal half. These two chaetal types are present through the body both in the neuropodia and in the notopodia. Adults specimens of the Cossura yacy sp. nov. have seven notopodial and five neuropodial chaetae in the 5th parapodium; nine notopodial and seven neuropodial chaetae in the 20th parapodium; five notopodial and six neuropodial chaetae in the 43th parapodium. Pygidium has three long anal cirri, reaching the fourth posterior segment.