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Family Stylasteridae Gray, 1847 Material collected: BBB 2016: St. 5; St. 9; St. 11; St. 12; St. 13; St. 16; St. 18; St. 21; St. 23; St. 25; St. 28; St. 29; St. 30; St. 33; St. 34; St. 35; St. 36; St. 40. Distribution: Seventeen stylasterid species are known to inhabit usually deep waters of the Argentinian shelf and slopes. The majority of them have been also recorded in the Burdwood bank region, but also other subantarctic waters. Specific information could be obtained from Cairns (1983) and Bernal et al. (2018). Remarks: Living and dead fragments of stylasterid colonies were collected. The material was not identified until species level yet. However, preliminary results showed that many collected specimens belong to the genus Errina, Errinopsis and Sporadopora. Epibiotic organisms were frequently attached to these colonies, as also noted by Schejter et al. (2017a, 2020). Moreover, they were conspicuous habitat-forming species of the animal forests recorded in the area (Schejter et al. 2020)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 209, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Cairns, S. D. (1983) Antarctic and subantarctic Stylasterina (Coelenterata: Hydrozoa). Biology of the Antarctic Seas XIII. Antarctic Research Series, 38, 61 - 164. https: // doi. org / 10.1029 / AR 038 p 0061","Bernal, M. C., Cairns, S. D., Penchaszadeh, P. & Lauretta, D. (2018) Errina argentina sp. nov., a new stylasterid (Hydrozoa: Stylasteridae) from Mar del Plata submarine canyon (Soutwest Atlantic). Marine Biodiversity, 49, 833 - 839. https: // doi. org / 10.1007 / s 12526 - 018 - 0861 - 1","Schejter, L., Martin, J. & Lovrich, G. (2017 a) Unveiling the submarine landscape of the Namuncura Marine Protected Area, Burdwood bank, SW Atlantic Ocean. Pan American Journal of Aquatic Sciences, 12 (3), 248 - 253.","Schejter, L., Genzano, G., Gaitan, E., Perez, C. D. & Bremec, C. S. (2020) Benthic communities in the Southwest Atlantic Ocean: Conservation value of animal forests at the Burdwood bank slope. Aquatic Conservation: Marine and Freshwater Ecosystems, 30, 426 - 439. https: // doi. org / 10.1002 / aqc. 3265"]}

Alcyonium sp. 2 Material examined: BBB 2016: St 13. Distribution: Between Tierra del Fuego and Burdwood bank, NDR (610 m). Remarks: colony bi-lobate, with polyps in conspicuous calyces and well developed anthocodial armature. Spindles from body wall resemble those on A. haddoni and A. yepayek, but A. haddoni lacks clubs in the inner layer and most clubs in A. yapayek have a central wart (Ofwegen et al. 2007). SEM analysis will allow us to cofirm if Alcyonium sp. 2 is, in fact, a new species., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 220, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Ofwegen, L. P., Haussermann, V. & Forsterra, G. (2007) The genus Alcyonium (Octocorallia: Alcyonacea: Alcyoniidae) in Chile. Zootaxa, 1607 (1), 1 - 19. https: // doi. org / 10.11646 / zootaxa. 1607.1.1"]}

Paragorgia arborea (Linnaeus, 1758) Material examined: BBB 2016: St. 13. Distribution: Western North Atlantic, East Canada to Cape Hatteras; Boreal Eastern Atlantic, northern Mid-Atlantic Ridge; Lusitanian-Mediterranean (Watling & Auster 2005); Norway to Nova Scotia, including Faroes Islands, Iceland and Greenland, 1330 m (Tendal 1992); off Crozet Islands, Indian Ocean (46°05’– 46°24.1’S, 49°37.0’– 50°37.1’E, 140–270 m) (Grasshoff 1979; D’Ambrosio et al. 1984); Aleutian Islands (Heifetz et al. 2005); Makarov Bay, Iturup Island, Sea of Okhotsk (Nedashkovskaya et al. 2005); Southern California (52°17’– 52°22’N, 160°40’– 160°34’E, 659–798 m), New Zealand (33°55’36”S– 52°17’22”S, 159°40’00– 177°54’30”E, 659–1525 m) (Sánchez 2005); Off Patagonia and Malvinas Islands (40°57’– 54°38’S, 56°52’– 63°00’W, 340– 1000 m) (Grasshoff 1979); Burdwood bank (54°31´S, 62°11´W, 330 m) (as Paragorgia sp.) (Auscavitch & Waller 2017); Drake Passage, 57°04´S, 67°30´W, 1400 m (as Paragorgia sp.) (Waller & Robinson 2011); off Staten Island (608 m) (present study). Remarks: According to Sánchez (2005), this species has a disjunct distribution between the Arctic and Antarctic, with no linking records. Auscavitch & Waller (2017) and Waller & Robinson (2011) cited Paragorgia sp. for the Drake passage and Burdwood bank, their identification at genus level is justified since the samplings were made by towed camera surveys. Deichmann (1936) said that according to Verrill (1922) this species is common off the fishing banks off Nova Scotia and Newfoundland., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 222, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Watling, L. & Auster, P. J. (2005) Distribution of deep-water Alcyonacea off the northeast coast of the United States. In: Freiwald, A. & Roberts, J. M. (Eds.), Cold-Water Corals and Ecosystems. Springer-Verlag, Berlin, pp. 279 - 296.","Tendal, O. S. (1992) The North Atlantic distribution of the octocoral Paragorgia arborea (L., 1758) (Cnidaria, Anthozoa). Sarsia, 77, 213 - 217. https: // doi. org / 10.1080 / 00364827.1992.10413506","Grasshoff, M. (1979) Zur bipolaren Verbreitung der Oktokoralle Paragorgia arborea (Cnidaria: Anthozoa: Scleraxonia). Senckenbergiana Maritima, 11 (3 / 6), 115 - 137.","D'Ambrosio, M., Guerriero, A. & Pietra, F. (1984) Arboxeniolide- 1, a New, Naturally Occurring Xeniolide Diterpenoid from the Gorgonian Paragorgia arborea of the Crozet Is. (S. Indian Ocean). Zeitschrift fur Naturforschung C, 39 (11 - 12), 1180 - 1183. https: // doi. org / 10.1515 / znc- 1984 - 11 - 1232","Heifetz, J., Wing, B. L., Stone, R. P., Malecha, P. W. & Courtney, D. L. (2005) Corals of the Aleutian Islands. Fisheries Oceanography, 14, 131 - 138. https: // doi. org / 10.1111 / j. 1365 - 2419.2005.00371. x","Nedashkovskaya, O., Kim, S., Lysenko, A., Frolova, G., Mikhailov, V. & Bae, K. (2005) Bizionia paragorgiae gen. Nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from the soft coral Paragorgia arborea. International Journal of Systematics and Evolutionary Microbiology, 55 (1), 375 - 378. https: // doi. org / 10.1099 / ijs. 0.63381 - 0","Sanchez, J. A. (2005) Systematics of the bubblegum corals (Cnidaria: Octocorallia: Paragorgiidae) with description of new species from New Zealand and the Eastern Pacific. Zootaxa, 1014 (1), 1 - 72. https: // doi. org / 10.11646 / zootaxa. 1014.1.1","Auscavitch, S. & Waller, R. (2017) Biogeographical patterns among deep sea megbenthic communities across the Drake Passage. Antarctic Science, 29 (6), 531 - 543. https: // doi. org / 10.1017 / S 0954102017000256","Deichmann, E. (1936) The Alcyonaria of the western part of the Atlantic Ocean. Memoirs of the Museum of Comparative Zoology at Harvard, 53, 1 - 317.","Verrill, A. E. (1922) Alcyonaria and Actinaria. Report of the Canadian Arctic Expeition, 8 (G), 1 - 164."]}

Ideogorgia laurae Pérez & Cordeiro, 2020 Material examined: BBB 2016: St. 25 (MACN-In 42334). Remarks: The genus was thought to be endemic to shallow-waters of southern Africa (30 to 73 m), with only one species described so far, Ideogorgia capensis Williams, 1992. The present new deep record (467 m) represents the first ocurrence of the genus in subantarctic waters and suggests early connections between these two distinct ocean basins. The material examined correspond to a new species recently described and deposited in the MACN (MACN-In 42334) (Pérez & Cordeiro 2020)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 221, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Perez, C. D. & Cordeiro, R. T. (2020) Ideogorgia laurae, an uncommon new octocoral species (Alcyonacea: Keroeididae) from a newly established Marine Protected Area at Burdwood bank, Argentina. Polar Biology, 43, 63 - 69. https: // doi. org / 10.1007 / s 00300 - 019 - 02604 - 2","Williams, G. C. (1992) The Alcyonacea of Southern Africa. Gorgonian octocorals (Coelenterata, Anthozoa). The Annals of the South African Museum, 101 (8), 181 - 296."]}

Bougainvillia macloviana Lesson, 1830 Material examined: BBB 2016: St. 23. Distribution: The polyp was recorded in Kerguelen Islands and South Africa (Millard 1977); Tierra del Fuego and Malvinas / Falkland Islands, as Perigonimus repens (Ritchie 1909; Jäderholm 1910: polyp) and Perigonimus octonus (Blanco 1994: polyp); recently in San Jorge Gulf, 45°54´S – 66°45´W (López Gappa et al. 2016). This is the first record at MPA Namuncurá I. Remarks: An unfertile fragment of a colony detached from its substrata was found., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 208, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Millard, N. A. H. (1977) Hydroids from the Kerguelen and Crozet shelves, collected by the cruise MD. 03 of the Marion-Dufresne. Annals of the South African Museum, 73, 1, 1 - 47.","Ritchie, J. (1909) Supplementary report on the hydroids of the Scottish National Antarctic Expedition. Transactions of the Royal Society of Edinburgh, 47, 65 - 101.","Jaderholm, E. (1910) Ueber die Hydroiden, welche Dr. C. Skottsberg, in den jahren 1907 - 1909 gesammelt. Arkiv for Zoologi, 6, 1 - 5.","Blanco, O. (1994) Enumeracion sistematica y distribucion geografica preliminar de los Hydroides de la Republica Argentina. Suborden Athecata (Gymnoblastea, Anthomedusae), Thecata (Calyptoblastea, Leptomedusae) y Limnomedusae. Revista del Museo de La Plata, Nueva Serie, 14 (161), 181 - 216.","Lopez Gappa, J., Liuzzi, M. G. & Genzano, G. (2016) Role of the clam Neilonella sulculata as hard substrate in muddy bottoms of San Jorge Gulf (Argentina, Southwest Atlantic). Marine Biology Research, 12 (8), 888 - 893. https: // doi. org / 10.1080 / 17451000.2016.1210809"]}

Heptaprimnoa patagonica Cairns, 2012 Material examined: BBB 2016: St. 21. Distribution: Southwestern Atlantic off Argentina: continental slope off Mar del Plata, (40°00’S, 56°02’W, 520 m), continental slope off Patagonia (44.872°S, 59.635°W, 1248 m; 45.068°S, 59.501°W, 776 m; 45.605°S, 59.773°W, 1232 m); Malvinas Islands (48°54’S, 56°52’W, 780 m); Burdwood bank (54°10’S, 56°40’W, 265 m) (Cairns 2012); Burdwood bank (767 m) (present study). Remarks: One of the paratypes of this species was obtained from the Burdwood bank (54°10’S, 56°40’W, 265 m) (Cairns 2012). Cairns’s specimens are uniplanar colonies and dichotomously branched with 8–10 polyps per whorls, whereas our specimen is a liriform colony with 7–8 polyps in each whorl., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 223, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884

Isosicyonis alba (Studer, 1879) Material examined: BBB 2016: St. 12; St. 13; St.17; St. 18; St. 21; St. 40 (MLP-Oi 4202). Distribution: Its distribution is known along the Argentinian shelf at more than 100 m depth (Studer 1879; Rie- mann-Zürneck 1980), South Shetland Islands (Carlgren 1949; Rodríguez & López-González 2008), Antarctic Peninsula (Fautin 1984) and Trinidad Channel (Chile) (Ridley 1882)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 215, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Studer, T. (1879) Zweite Abtheilung der * Antozoa polyactinia *, welche wahrend der Reise S. M. S. Corvette Gazelle um die Erde gesammelt wurden. Monatsberichte der Akademie der Wissenschaften, Berlin, 1879, 524 - 550.","Carlgren, O. (1949) A survey of the Ptychodactiaria, Corallimorpharia and Actiniaria. Kungliga Svenska Vetenskapsakademiens Handlingar, 1 (1), 1 - 121.","Rodriguez, E. & Lopez-Gonzalez, P. J. (2008) The gastropod-symbiotic sea anemone genus Isosicyonis Carlgren, 1927 (Actiniaria: Actiniidae): a new species from the Weddell Sea (Antarctica) that clarifies the taxonomic position of the genus. Scientia Marina, 72 (1), 73 - 86. https: // doi. org / 10.3989 / scimar. 2008.72 n 173","Fautin, D. G. (1984) More Antarctic and Subantarctic sea anemones (Coelenterata: Corallimorpharia and Actiniaria). Biology of the Antarctic Seas XVI, Antarctic Research Series, 41, 1 - 42. https: // doi. org / 10.1002 / 9781118666579. ch 1","Ridley, S. O. (1882) Zoological collections made during the survey of H. M. S.`Alert' X. Coelenterata. Proceedings of the Zoological Society of London, 1882, 101 - 107."]}

Alcyonium patagonicum (May, 1899) Material examined: BBB 2016: St. 5. Distribution: Argentinean Patagonian shelf, 44°14’S, 61°23’W (110 m) (Verseveldt & Ofwegen 1992), Beagle Channel (127 m) (present study). Remarks: Digitiform colonies attached to bivalve shells., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 219, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["May, W. (1899) Alcyonarien. In: Hamburger Magalhaensische Sammelreise, Friederichsen, L. & Co., Hamburg, pp. 1 - 22.","Verseveldt, J. & Ofwegen, L. P. (1992) New and redescribed species of Alcyonium Linnaeus, 1758 (Anthozoa: Alcyonacea). Zoologische Verhandelingen Leiden, 66 (7), 155 - 181."]}

Balanophyllia malouinensis Squires, 1961 Material examined: BBB 2016: St. 12; St. 13; St. 16; St. 18; St. 21; St. 23; St. 25; St. 36. PD BB 2017: St. 13; St. 14; St. 16; St. 31; St. 33; St. 34; St. 43 (Fig. 2H) (MACN-In: 41666, 41667, 41668, 41669, 41670, 41671, 41672, 41673). Distribution: Off Tierra del Fuego, Malvinas / Falkland Islands and Scotia Ridge between Burdwood bank and South Georgia, Drake Passage off Cape Horn, off Isla Desolación, Chile, 53ºS (Cairns 1982; Cairns et al. 2005). Remarks: This species was the most common scleractinid coral of the studied region. The collected specimens presented several epibionts (cnidarians, crustaceans) and were also used as settlement substrate for other species in the area. See Schejter & Bremec (2019) for detailed information on Scleractinia collected during these expeditions., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 217, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Cairns, S. D. (1982) Antarctic and Subantarctic Scleractinia. Biology of the Antarctic Seas XI. Antarctic Researsch Series, 34, 1 - 74. https: // doi. org / 10.1029 / AR 034 p 0001","Cairns, S. D., Haeusermann, V. & Forsterra, G. (2005) A review of the Scleractinia (Cnidaria: Anthozoa) of Chile, with the description of two new species. Zootaxa, 1018 (1), 15 - 46. https: // doi. org / 10.11646 / zootaxa. 1018.1.2","Schejter, L. & Bremec, C. S. (2019) Stony corals (Anthozoa Scleractinia) of Burdwood Bank and neighbouring areas, SW Atlantic Ocean. Scientia Marina, 83 (3), 247 - 260. https: // doi. org / 10.3989 / scimar. 04863.10 A"]}

Caryophyllia coronula Cairns & Polonio, 2013 Material examined: PD BB 2017: St. 31; St. 34 (MACN-In 41675, 41676). Distribution: Continental slope off Golfo San Jorge, Argentina, 797–1553 m (Cairns & Polonio 2013). Remarks. The present finding representing the second mention of the species, extending the southern distribution limit to Burdwood bank (53,66668°S and 61,63667°W) (see Schejter & Bremec, 2019)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 217, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Cairns, S. D. & Polonio, V. (2013) New records of deep-water Scleractinia off Argentina and the Falkland Islands. Zootaxa, 3691 (1), 58 - 86. https: // doi. org / 10.11646 / zootaxa. 3691.1.2","Schejter, L. & Bremec, C. S. (2019) Stony corals (Anthozoa Scleractinia) of Burdwood Bank and neighbouring areas, SW Atlantic Ocean. Scientia Marina, 83 (3), 247 - 260. https: // doi. org / 10.3989 / scimar. 04863.10 A"]}

Tulpa tulipifera (Allman, 1888) Material examined: BBB 2016: St. 16; St. 18; St. 23; St. 28; St. 36; St. 40 (MACN-In: 43468, 43469, 43470, 43471, 43472). Distribution: This species was reported in Heard Island, 52°04’S, 71°22E, Burdwood bank and Malvinas /Faklands Islands as Campanularia tulipifera (Jäderholm, 1905); it is distributed from 41°S to 56°S (Oliveira et al. 2016). Remarks: Very abundant colonies were found, some of them with gonothecae and growing on soft-corals., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 214, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Jaderholm, E. (1905) Hydroiden aus antarktischen und subantarktischen Meeren gesammelt von der schwedischen Sudpolarexpedition. Wissenschaftliche Ergebnisse der Schwedischen Sudpolar-Expedition 1901 - 1903, 5, 1 - 41.","Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Bolocera kerguelensis Studer, 1879 Material examined: BBB 2016: St. 11; St. 12; St. 13; St. 17; St. 18; St. 21; St. 23; St. 36; St. 40 (Fig. 2K) (MLP-Oi 4203). Distribution: It is a common species in the area, previously recorded in the Argentinean shelf (Riemann-Zürneck 1980), Straits of Magellan (Chile), Drake Passage and Antarctic Peninsula (McMurrich 1893; Dunn 1983), and near the Burdwood bank (Dunn 1983). It was also recorded by Studer (1879) northwest of Kerguelen (48º30’S, 69º40’E, 219 m), by Carlgren (1938) in False Bay (34º15’S, 17º57’E, 91 m) and Agulhas Bank (35ºS, 20’E, 73–77 m). This is the first record in the MPA Namuncurá I., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 215, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Studer, T. (1879) Zweite Abtheilung der * Antozoa polyactinia *, welche wahrend der Reise S. M. S. Corvette Gazelle um die Erde gesammelt wurden. Monatsberichte der Akademie der Wissenschaften, Berlin, 1879, 524 - 550.","Riemann-Zurneck, K. (1980) Actiniaria des Sudwestatlantik V. Bolocera, Isotealia, Isosicyonis (Actiniidae). Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut, 77, 19 - 33.","McMurrich, J. P. (1893) Report on the Actiniae collected by the United States Fish Commission Steamer Albatross during the winter of 1887 - 1888. Proceedings of the United States National Museum, 16 (930), 119 - 216.","Dunn, D. F. (1983) Some Antarctic and sub-antarctic sea anemones (Coelenterata: Ptychodactiaria and Actiniaria). Biology of the Antarctic Seas XIV, Antarctic Research Series, 39, 1 - 67. https: // doi. org / 10.1029 / AR 039 p 0001","Carlgren, O. (1938) South African Actiniaria and Zoantharia. Kungliga Svenska Vetenskapsakademiens Handlingar, 17 (3), 1 - 148."]}

Hebella sp. Material examined: BBB 2016: St. 5; St. 27; St. 32; St. 38; St. 39. Remarks: Scarce colonies attached on other hydroids (Abietinella operculata and S. subdichotomus) and on tubes of the polychaetes Chaetopterus antarcticus were found. Alike the genus Filellum, identification of Hebella to specific level is not possible when the material lacks reproductive structures. However the nominal species Hebella striata Allman, 1888 was widely reported in Argentinean continental shelf., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 210, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884

Phialella chilensis (Hartlaub, 1905) Material examined: BBB 2016: St. 23. GARCÍA 2015: St. 4. Distribution: Phialella chilensis has originally been described from Calbuco, Chile (Vervoort 1972). The species has been reported in southwestern Atlantic from 34°S to 55°S by Jäderholm (1905) and Ritchie (1909) as Campanulina chilensis and by Blanco et al. (2000). Remarks: Small and well preserved colonies were found detached from substrate., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on pages 213-214, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Hartlaub, C. (1905) Die Hydroiden der Magalhaensischen Region und chilenischen Kuste. In: Fauna chilensis. Zoologische Jahrbucher, Supplement 6 (3), 497 - 714.","Vervoort, W. (1972) Hydroids from the Theta, Vema and Yelcho cruises of the Lamont Doherty Geological Observatory. Zoologische Verhandelingen, 120, 1 - 47.","Jaderholm, E. (1905) Hydroiden aus antarktischen und subantarktischen Meeren gesammelt von der schwedischen Sudpolarexpedition. Wissenschaftliche Ergebnisse der Schwedischen Sudpolar-Expedition 1901 - 1903, 5, 1 - 41.","Ritchie, J. (1909) Supplementary report on the hydroids of the Scottish National Antarctic Expedition. Transactions of the Royal Society of Edinburgh, 47, 65 - 101.","Blanco, O., Zamponi, M. O. & Genzano, G. N. (2000) Campanuliniidae de la Argentina (Coelenterata; Hydrozoa). Revista del Museo de La Plata, Nueva Serie, Zoologia, 14 (163), 267 - 278."]}

Caryophyllia squiresi Cairns, 1982 Material examined: BBB 2016: St. 13; St. 18; St. 21; St. 25. PD BB 2017: St. 13; St. 14; St. 31; St. 34 (MACN-In: 41677, 41678, 41679, 41680, 41681, 41682, 41683, 41684, 41685). Distribution: Off Tierra del Fuego and Malvinas (Falkland) Islands at 406–659 m, recent records extended its range slightly north (42ºS) and expand its bathymetric range (Cairns & Polonio 2013). Remarks: Some individuals were settled on Balanophyllia malouinensis. This species was recorded at MPA Namuncurá II (see Schejter & Bremec 2019)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 217, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Cairns, S. D. (1982) Antarctic and Subantarctic Scleractinia. Biology of the Antarctic Seas XI. Antarctic Researsch Series, 34, 1 - 74. https: // doi. org / 10.1029 / AR 034 p 0001","Cairns, S. D. & Polonio, V. (2013) New records of deep-water Scleractinia off Argentina and the Falkland Islands. Zootaxa, 3691 (1), 58 - 86. https: // doi. org / 10.11646 / zootaxa. 3691.1.2","Schejter, L. & Bremec, C. S. (2019) Stony corals (Anthozoa Scleractinia) of Burdwood Bank and neighbouring areas, SW Atlantic Ocean. Scientia Marina, 83 (3), 247 - 260. https: // doi. org / 10.3989 / scimar. 04863.10 A"]}

Thouarella (Epithouarella) chilensis Kükenthal, 1908 Material examined: BBB 2016: St. 12; St. 13; St. 23; St. 26; St. 35; St. 36; St. 39; St. 40. Distribution: Tierra del Fuego, Argentina (54°34′S, 65°50′W, 118 m) (as T. antarctica) (Cairns & Bayer 2009); Iquique, Chile (Kükenthal 1919, as T. (Epithouarella) chilensis); Crozet Island, sub-Antarctic (46˚5’S, 51˚52’E, 1005 m), Sandwich Islands (56˚44’17”S, 26˚58’36”W, 302–375 m), Estados (54˚34’S, 64˚00’W, 84 m), Indian Ocean (53°18’S, 73°19’E, 250 m), Weddell Sea (71°05.9’S, 12°34’W, 522–531 m), Patagonian Shelf (40˚57’S, 56˚52’W, 200 m), Burdwood bank (52°59’S, 44°22.7’E, 295– 325 m) (Taylor et al. 2013; Schejter et al. 2016a); off Staten Is., Burdwood bank (125–681 m) (present study). Remarks: Synonyms at the area: Thouarella antarctica sensu Cairns & Bayer 2009 (= T. chilensis). As for most of Antactic primnoids, available information about T. chilensis is still limited to taxonomic works; a complete list of all these studies is given by Taylor et al. (2013), which recorded this species at the Burdwood bank area for the first time., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 225, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Cairns, S. D. & Bayer, F. M. (2009) A generic revision and phylogenetic analysis of the Primnoidae (Cnidaria: Octocorallia). Smithsonian Contributions to Zoology, 629, 1 - 79. https: // doi. org / 10.5479 / si. 00810282.629","Kukenthal, W. (1919) Gorgonaria. Wissenschaftliche Ergebnisse der Tiefsee-Expedition Valdivia, 13 (2), 1 - 946.","Taylor, M. L., Cairns, S. D., Agnew, D. & Rogers, A. D. (2013) A revision of the genus Thouarella Gray, 1870 (Octocorallia: Primnoidae), including an illustrated dichotomous key, a new species description, and comments on Plumarella Gray, 1870 and Dasystenella, Versluys, 1906. Zootaxa, 3602 (1), 1 - 105. https: // doi. org / 10.11646 / zootaxa. 3602.1.1","Schejter, L., Rimondino, C., Chiesa, I., Diaz de Astarloa, J. M., Doti, B. L., Elias, R., Escolar, M., Genzano, G., Lopez Gappa, J., Tatian, M., Zelaya, D. G., Cristobo, J., Perez, C. D., Cordeiro, R. T. & Bremec, C. S. (2016 a) Namuncura Marine Protected Area: an oceanic hot spot of benthic biodiversity at Burdwood bank, Argentina. Polar Biology, 39, 2373 - 2386. https: // doi. org / 10.1007 / s 00300 - 016 - 1913 - 2"]}

Thouarella (Epithouarella) viridis Zapata-Guardiola & Lopez-González, 2010 Material examined: BBB 2016: St. 18. Distribution: From South Georgia Island area (53º23’S, 42º42´W, 312–321 m; 54º24´S, 35º36´W, 278–279 m) and south east of Malvinas Islands, Burdwood bank (54°30´S, 56°08´W, 286–291 m) (Zapata Guardiola & López-González 2010a); Sars Seamount (59°42´S, 68°49´W, 520 m); Shackleton Fracture Zone (59°19.5S, 60°06.25W, 2295 m), off Cape Horn (57°00.33S, 67°35.1W, 450 m, 57°13.81S, 67°02.32W, 1100 m); Burdwood bank (54°31´S, 62°11´W, 330 m); Elephant Island (61°15´S, 56°24´W, 450 m) (as Thouarella cf. viridis) (Auscavitch & Waller 2017); South Georgia (54˚30’S, 39˚20’W, 659– 686 m), Tierra del Fuego, Argentina (54˚22’S, 64˚42’W, 106–110 m), Patagonian Shelf (42˚52’S, 58˚38’W, 1200 m), Malvinas Islands (52˚40’S, 60˚39’W, 405 m), Burdwood bank (54˚57’S, 56˚54’W, 500 m) (Taylor et al. 2013); Burdwood bank (607 m) (present study). Remarks: Zapata Guardiola & López-González (2010a) pointed that T. viridis resembles polyps of the genus Amphilaphis due to the prominent apical keel on the inner surface of the opercular scales. However, the branching pattern and the reduction in size of the basal body scales allocate this species among the Thouarella species, in which the presence of keels on the inner surface of operculars has been also documented., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 225, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Auscavitch, S. & Waller, R. (2017) Biogeographical patterns among deep sea megbenthic communities across the Drake Passage. Antarctic Science, 29 (6), 531 - 543. https: // doi. org / 10.1017 / S 0954102017000256","Taylor, M. L., Cairns, S. D., Agnew, D. & Rogers, A. D. (2013) A revision of the genus Thouarella Gray, 1870 (Octocorallia: Primnoidae), including an illustrated dichotomous key, a new species description, and comments on Plumarella Gray, 1870 and Dasystenella, Versluys, 1906. Zootaxa, 3602 (1), 1 - 105. https: // doi. org / 10.11646 / zootaxa. 3602.1.1"]}

Modeeria rotunda (Quoy & Gaimard, 1827) Material examined: GARCÍA 2015: St. 17 (MACN-In: 43467). Distribution: Polyp widely distributed between boreal and subantarctic waters, in South America the species was reported in Pacific Ocean, Chile, from 41° to 54°S and Atlantic Ocean, Argentina, at 42.50°S 62.45°W and near to Malvinas (Falkland) Islands (Oliveira et al. 2016). This is the first record at MPA Namuncurá I. Remarks: Synonyms in the area: Stegopoma fastigiatum (Vervoort 1972; Blanco 1994)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 211, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1","Vervoort, W. (1972) Hydroids from the Theta, Vema and Yelcho cruises of the Lamont Doherty Geological Observatory. Zoologische Verhandelingen, 120, 1 - 47.","Blanco, O. (1994) Enumeracion sistematica y distribucion geografica preliminar de los Hydroides de la Republica Argentina. Suborden Athecata (Gymnoblastea, Anthomedusae), Thecata (Calyptoblastea, Leptomedusae) y Limnomedusae. Revista del Museo de La Plata, Nueva Serie, 14 (161), 181 - 216."]}

Rhodalia miranda Haeckel, 1888 Material examined: PD BB 2017: St. 30; St. 31. Distribution: Atlantic Ocean, Uruguay-Argentina, from 35º to 56ºS on slope (Riemann-Zurneck 1991). Remarks: Epibenthic colonial siphonophorae with demersal habit were found., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 215, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Riemann-Zurneck, K. (1991) The benthic deep-water siphonophore Rhodalia miranda and other coelenterates in the south-west Atlantic: ecological and oceanographical implications. Hydrobiologia, 216 (217), 481 - 487. https: // doi. org / 10.1007 / BF 00026502"]}

Flabellum thouarsii Milne Edwards & Haime, 1848 Material examined: BBB 2016: St. 12; St. 17; St. 21; St. 36. PD BB 2017: St. 13; St. 16; St. 36 (MACN-In: 41708, 41709, 41710, 41711, 41712, 41713, 41714). Distribution: Entire coast of Argentina from Río de la Plata to Tierra del Fuego, Malvinas (Falkland) Islands (Cairns & Polonio 2013). Remarks: This species was previously recorded at Burdwood bank (Schejter et al. 2016a). It was recorded in the present study at MPAs Namuncurá I and II (see also Schejter & Bremec 2019 as F. thouarsi by mispelling)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 218, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Cairns, S. D. & Polonio, V. (2013) New records of deep-water Scleractinia off Argentina and the Falkland Islands. Zootaxa, 3691 (1), 58 - 86. https: // doi. org / 10.11646 / zootaxa. 3691.1.2","Schejter, L., Rimondino, C., Chiesa, I., Diaz de Astarloa, J. M., Doti, B. L., Elias, R., Escolar, M., Genzano, G., Lopez Gappa, J., Tatian, M., Zelaya, D. G., Cristobo, J., Perez, C. D., Cordeiro, R. T. & Bremec, C. S. (2016 a) Namuncura Marine Protected Area: an oceanic hot spot of benthic biodiversity at Burdwood bank, Argentina. Polar Biology, 39, 2373 - 2386. https: // doi. org / 10.1007 / s 00300 - 016 - 1913 - 2","Schejter, L. & Bremec, C. S. (2019) Stony corals (Anthozoa Scleractinia) of Burdwood Bank and neighbouring areas, SW Atlantic Ocean. Scientia Marina, 83 (3), 247 - 260. https: // doi. org / 10.3989 / scimar. 04863.10 A"]}

Sertularella cylindritheca (Allman, 1888) Material examined: BBB 2016: St. 12; St. 13. Distribution: The species occurs along both sides of the South Atlantic. In southwestern Atlantic the species had been frequently reported in Brazilian and Argentinean coasts (Oliveira et al. 2016). Remarks: Immature colonies were found detached from the substrate., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 212, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Campanularia sp. Material examined: BBB 2016: St. 4; St. 23; St. 32. Remarks: We found stems with scarce hidrothecae and lacking gonothecae growing on the hydroids Symplectoscyphus subdichotomus and Halecium jaederholmi and bryozooan colonies. The identification to specific level was not possible.

Halecium delicatulum Coughtrey, 1876 Material examined: BBB 2016: St. 4; St. 34; St. 39. GARCÍA 2015: St. 4; St. 5, St. 6 (MACN-In: 43477). Distribution: circumpolar distribution in subtropical and temperate waters (Vervoort 1972). This species was frequently reported in the southwestern Atlantic Ocean. This is the first record of this species in MPA Namuncurá I. Remarks: Unfertile colonies growing on plumularids hydroids were found., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 211, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Vervoort, W. (1972) Hydroids from the Theta, Vema and Yelcho cruises of the Lamont Doherty Geological Observatory. Zoologische Verhandelingen, 120, 1 - 47."]}

Eudendrium ramosum (Linnaeus, 1758) Material examined: BBB 2016: St. 12; St. 18 (MACN-In 43478). Distribution: This cosmopolitan species is widely distributed in the southwestern Atlantic Ocean (see Oliveira et al. 2016). Remarks: Fertile male colonies recorded at the MPA Namuncurá II were observed., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 208, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Lafoea dumosa (Fleming, 1820) Material examined: BBB 2016: St. 5; St. 12; St. 23; St. 28; St. 31; St. 32; St. 33; St. 34; St. 39. GARCIA 2015: St. 2; St. 3; St. 6 (Fig. 2J) (MACN-In: 43483, 43484). Distribution: Cosmopolitan. Species widely distributed along southwestern Atlantic Ocean (see Blanco 1994; Oliveira et al. 2016). Remarks: Abundant, unfertile colonies were widely found in all analyzed areas, usually as epizoics on the hydroid S. subdichotomus. Also recorded in the area as Lafoea fruticosa (see Oliveira et al. 2016)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 210, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Blanco, O. (1994) Enumeracion sistematica y distribucion geografica preliminar de los Hydroides de la Republica Argentina. Suborden Athecata (Gymnoblastea, Anthomedusae), Thecata (Calyptoblastea, Leptomedusae) y Limnomedusae. Revista del Museo de La Plata, Nueva Serie, 14 (161), 181 - 216.","Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Nidalia sp. Material examined: BBB 2016: St. 16. Remarks: The genus has been reported in the Indian Ocean, Western Atlantic, and Western Pacific (Pérez et al. 2011), but there were no records until present in subantarctic waters. The previous bathymetric records of the genus reached 549 m depths (N. dissidens in Strait of Florida). Herein, 1000 m represents the new lower depth for the genus. Pérez et al. (2011) cited N. occidentalis (mushroom-shaped polyparium and without sclerites in the introvert) and Nidalia sp. for Brazilian coast. Using the key to the genus of Verseveldt & Bayer (1988), our specimen would fit N. simpsoni, but our morphotype has fewer rows of crown spindles (10–14 to 15–20 in N. simpsoni), more spindles at the points (10–19 to 6–10) and points not in chevron. In addition, N. simpsoni was described from Indonesian Archipelago and Palau Islands. Our specimen has a torch-like capitulum and introvert with numerous small dumbbells as Nidalia sp. sensu Pérez et al. (2011), but differs in having fewer rows of crown spindles (10–14 to 18), more spindles per point (10–19 to 6–8) and smaller spindles from crown and stalk. Herein, we consider it a possible new species., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 221, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Perez, C. D., Neves, B. M. & Oliveira, D. H. (2011) New records of octocorals (Cnidaria: Anthozoa) from the Brazilian coast. Aquatic Biology, 13, 203 - 214. https: // doi. org / 10.3354 / ab 00363","Verseveldt, J. & Bayer, F. (1988) A revision of the genera Bellonella, Eleutherobia, Nidalia and Nidaliopsis (Octocorallia: Alcyoniidae and Nidaliidae), with descriptions of two new genera. Zoologische Verhandelingen Leiden, 245, 1 - 131."]}

Actinostola crassicornis (Hertwig, 1882) Material examined: BBB 2016: St. 9; St. 11; St. 13; St. 17; St. 18; St. 23; St. 30; St. 31; St. 36; St. 40 (Fig. 2B) (MLP-Oi 4205). Distribution: Widely distributed in the southwest Atlantic Ocean including the MPA Namuncurá I/ Burdwood bank (Riemann-Zürneck, 1978). Also recorded by Carlgren (1898) in the Magellan Strait (52º07’S, 70º26’W, 274 m), by McMurrich (1904) in Calbuco (Chile) and other coastal localities of Chile (41º36 – 41º51’S, 25– 278 m) by Carlgren (1959)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on pages 215-216, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Riemann-Zurneck, K. (1978) Actiniaria des Sudwestatlantik IV. Actinostola crassicornis (Hertwig, 1882) mit uner Diskussion verwandter Arten. Veroffentlichungen des Institutes fur Meeresforschung, Bremerch, 17, 65 - 85.","Carlgren, O. (1898) Zoantharien. Hamburger Magalhaensische Sammelreise, 4 (1), 1 - 48.","McMurrich, J. P. (1904) The Actiniae of the Plate collection. Zoologische Jahrbucher Jena, 6 (Supplement 2), 215 - 306.","Carlgren, O. (1959) Corallimorpharia and Actiniaria with description of a new genus and species from Peru. Reports of the Lund University Chile Expedition 1948 - 49 38. Arkiv fur Zoologi, 71 (6), 1 - 38."]}

Australisis sarmentosa Bayer & Stefani, 1987 Material examined: BBB 2016: St. 21. Distribution: South Shetland Islands, 61°19’– 61°21’S, 56°28’– 56°27’S, 403 m; off South Georgia: 54°29’S, 39°22’W, 659–686 m; 55°00.6’S, 37°42.6’W, 494–501 m; 53°27.1’S, 41°39.2’W, 371–424 m (Bayer & Stefani 1987). Remarks: This species was described 30 years ago, and this finding represents the first record after its description. The present record is the deepest for the species (785 m) and its first occurrence in the Burdwood bank area at MPA Namuncurá II., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on pages 221-222, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Bayer, F. M. & Stefani, J. (1987) New and previously known taxa of isidid octocorals (Coelenterata: Gorgonacea) partly from Antarctic waters. Proceedings of the Biological Society of Washington, 100 (4), 937 - 991."]}

Primnoisis (Primnoisis) antarctica Wright & Studer, 1889 Material examined: BBB 2016: St. 28. GARCÍA 2015: St. 17bis. (MACN-In: 43513) Distribution: Marion Islands, Off Prince Edward Island, 567 m (Wright & Studer 1889); Weddel Sea (71°05’S, 13°01’E), 60–500 m (Orejas et al. 2003); Antarctic Peninsula, (64°49.4’S to 64°49.5’S), 120–148 m (Bayer & Stefani, 1987); Burdwood bank (125–177 m) (present study). Remarks: This is a common Antarctic species, likely being a pioneer species in bottoms recently disturbed (Orejas et al. 2000). It is also one of the few Antarctic octocorals for which information on its feeding behavior is available (Orejas et al. 2003). This is the first record of the species in the Burdwood bank and at MPA Namuncurá I.

Thouarella (Thouarella) variabilis Wright & Studer, 1889 Material examined: BBB 2016: St. 16; St. 18. Distribution: Heard Island, 274 m, Prince Edward Island, 567 m, (Wright & Studer 1889); Antarctic, 350– 385m (Kükenthal 1919); Renaud Island, Biscoe Islands, Antarctic Peninsula (65˚30’S, 67˚31’W, 180 m; 76˚00’S, 55˚00’W, 457 m), Antipodes Island, New Zealand, (49˚51’S, 178˚35’E, 2010–2100 m) (Taylor et al. 2013); Burdwood bank (607–1000 m) (present study). Remarks: Synonyms: T. variabilis var. gracilis Wright & Studer, 1889. Thouarella variabilis was addressed in a recent study, testing its potential in paleorecords for changes in environmental conditions (Martinez-Dios et al. 2016). This species is one of the few Antarctic primnoids with some available ecological data in the literature. It was described in terms of its reproductive biology (Brito et al. 1995) and had its feeding behavior related to resuspension processes (Orejas et al. 2000). This is the first record of the species at Burdwood bank and at MPA Namuncurá II.

Hincksella stolonifera (Hartlaub, 1904) Material examined: BBB 2016: St. 12; St. 13; St. 23 (MACN-In: 43446, 43447, 43448, 43449, 43450). Distribution: Jäderholm (1905) reported this species in Robertson Island, Antarctic sector, 400 m depth as Sertularia stolonifera. This is the first record in the Argentinean continental shelf including MPA Namuncurá I. Remarks: We found abundant unfertile colonies detached from substratum., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 210, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Jaderholm, E. (1905) Hydroiden aus antarktischen und subantarktischen Meeren gesammelt von der schwedischen Sudpolarexpedition. Wissenschaftliche Ergebnisse der Schwedischen Sudpolar-Expedition 1901 - 1903, 5, 1 - 41."]}

Plumularia sp. Material examined: BBB 2016: St. 4; St. 11. Remarks: Numerous hydrocauluses with scarce and deteriorated hidrocladia were found. The identification to specific level was not possible.

Sphaeralcyon cf. scotti Material examined: BBB 2016: St. 13. Remarks: The genus Sphaeralcyon has three known species: S. shackletoni (distributed off Elephant Island, at the southern branch of the Scotia Arc, 3966–3974 m); S. weddellensis (recorded at eastern Weddell Sea, 418– 485 m) and S. scotti (distributed off South Sandwich Islands, Scotia Sea, 289– 308 m) (López-González & Gili 2000 2005). The morphotype of the present study was sampled between Staten Is. and Burdwood bank (608 m) and represents the first record for the genus in Argentine waters. Sphaeralcyon sp. presentes a well developed anthocodial armature, short spindles with large cone-like tubercles in stalk surface and spheroids absent, whereas S. weddellensis has reduced anthocodial armature and well developed tuberculate spheroids; and S. shackletoni has stalk surface sclerites ovoids with short tubercles. Our two specimens would fit S. scotti but the anthocodial armature is not clearly separated from the bases of the tentacles and the sclerites of the stalk suface are regular spindles with large cone-like turbercles, while S. scotti has anthocodial armature distinctly separated from the bases of the tentacles and the sclerites of the stalk surface are irregular rods with large cone-like turbercles. The abbreviation cf. (short for the Latin: confer/conferatur, both meaning “compare”) is used here to express a possible identity, but it’s necessary to analyze more sclerites to confirm the status of the specimens., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 220, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Lopez-Gonzalez, P. J. & Gili, J. M. (2000) A new octocoral genus (Cnidaria: Anthozoa) from Antarctic waters. Polar Biology, 23, 452 - 458. https: // doi. org / 10.1007 / s 003009900105"]}

Symplectoscyphus subdichotomus (Kirchenpauer, 1884) Material examined: BBB 2016: St. 4; St. 5; St. 9; St. 12; St. 13; St. 16; St. 18; St. 23; St. 27; St. 28; St. 31; St. 32; St. 33; St. 34; St. 35; St. 36; St. 38; St. 39 (Fig. 2A) (MACN-In: 43479, 43480, 43481). Distribution: The species presents a broad geographic distribution in southwestern Atlantic, between 29º– 56°S, reported as Sertularella johnstoni; Sertularella subdichotoma; Sertularella johnstoni (Oliveira et al. 2016 and references therein). Remarks: Species were frequently found in all analyzed sites, usually conforming dense and mature clumps. Colonies were found attached on bryozoans, Chaetopterus antarcticus tubes, and the hydroids Halecium jaederholmi, Synthecium protectum and Hincksella stolonifera., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 212, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Kirchenpauer, G. H. (1884) Nordische Gattungen und Arten von Sertulariden. Abhandlungen aus dem Gebiete der Naturwissenschaften, Hamburg, 8 (3), 1 - 54.","Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Alcyonium haddoni Wright & Studer, 1889 Material examined: BBB 2016: St. 23; St. 27; St. 32; St. 40. Distribution: Off Río de la Plata (36º06’S 53º18’W; 278–282 m) (Verseveldt 1967); Uruguay (35º24’S 52º30’W; 400 m) (Castro 1990); Chile (48º30’S 74º30’W; 320 m) (Wright & Studer 1889) 43°09’02.1” S, 73°35’30.9” W to 51°36’20.8” S, 73°55’33.8” W (6–30 m) (Ofwegen et al. 2007); Burdwood bank (Argentina) (90–422 m) (present study). Remarks: Not Alcyonium haddoni: Pérez & Zamponi 2004. Ofwegen et al. (2007) question Verseveldt’s (1967) identification and restrict the species distribution to Chilean waters, although Castro (1990) agrees with Verseveldt and lists it off Uruguay. The current records represent the first occurrence for the Burdwood region (including both MPAs), filling gaps in the amphiamerican distribution of the species, within the southern region of the South American continent (35º24’S, 52º30’W to 43°09’02.1”S, 73°35’30.9”W). The specimens sampled at station 40 represent the deepest record for the species (422 m). Specimens were found inhabiting rubbles and biogenic substrata (gorgonians, primnoids and hydrocorals skeletons)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on pages 218-219, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Wright, E. P. & Studer, T. (1889) Report onthe Alcyonaria collected by H. M. S. Challenger during the years 1873 - 1876. Report on the Scientific Results of the voyage of H. M. S. Challenger, Zoology, 31, 1 - 314.","Verseveldt, J. (1967) The Octocorallia collected by R / V \" Vema \" in the Atlantic Ocean. American Museum Novitates, 2282, 1 - 19.","Castro, C. B. (1990) Revisao dos Octocorallia (Cnidaria, Anthozoa) do litoral Sul-Americano: da foz do Rio Amazonas a foz do Rio da Prata. PhD Thesis, Universidade de Sao Paulo, Sao Paulo, 343 pp.","Ofwegen, L. P., Haussermann, V. & Forsterra, G. (2007) The genus Alcyonium (Octocorallia: Alcyonacea: Alcyoniidae) in Chile. Zootaxa, 1607 (1), 1 - 19. https: // doi. org / 10.11646 / zootaxa. 1607.1.1","Perez, C. D. & Zamponi, M. O. (2004) New records of octocorals (Cnidaria, Anthozoa) from Southwestern Atlantic Ocean. Zoogeographic considerations. Zootaxa, 630, 1 - 12. https: // doi. org / 10.11646 / zootaxa. 630.1.1"]}

Bayergorgia vermidoma Williams & Lopez-Gonzalez, 2005 Material examined: BBB 2016: St. 12; St. 13; St. 18; St. 21; St. 23; St. 26; St. 36; St. 38; St. 40. PD BB 2017: St. 14; St. 21; St. 43 (MACN-In: 43486, 43487). Distribution: Drake Passage (61°26.08’S, 58°06.2’W, 1047–1227 m); Elephant Island, (61°18.14’S, 56°8.27’W, 281.1–288.6 m); Shag Rocks (53°23.59’S, 42°41.78’W, 223.6–307 m) Antarctic Peninsula, South Shetland Is.; South Georgia Is. (54°29’S, 39°22’W, 659–686 m); South Orkney Is. (60°22’S, 46°50’W, 298–403 m) (Williams & López-González 2005); off Cape Horn (57°00.33’S, 67°35.1’W, 450 m; 57°13.81’S, 67°02.32’W 1100 m); Burdwood bank 54°31´S, 62°11´W 330 m as Clavularia sp. (Schejter et al. 2016a).); Elephant Island (61°15´S, 56°24´W, 450 m) (Auscavitch & Waller 2017); Drake Passage, 57°04´S, 67°30´W, 850 m (Waller & Robinson 2011 as Bayergorgia sp.); off Tierra del Fuego, Burdwood bank (130–785 m) (present study). Remarks: The original diagnosis of the species does not include branched specimens (Williams & López-González 2005). Although the authors discuss some branched forms, it is unlikely these specimens correspond to a different new species. Besides the presence of branching, we could not find clear boundaries between those two morphotypes either in the specimens examined herein or in specimens from other areas (unpublished data). Thus, we suggest the emendation of the diagnosis of B. vermidoma to include both branched and unbranched forms. Some of the studied specimens presented epibionts, mainly other cnidarians (see Schejter et al. 2020)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 221, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Williams, G. C. & Lopez-Gonzalez, P. J. (2005) A new genus and species of gorgonian octocoral (Anthozoa: Plexauridae) from Antarctic waters. Proceedings of the California Academy of Sciences, 56 (26), 379 - 390.","Schejter, L., Rimondino, C., Chiesa, I., Diaz de Astarloa, J. M., Doti, B. L., Elias, R., Escolar, M., Genzano, G., Lopez Gappa, J., Tatian, M., Zelaya, D. G., Cristobo, J., Perez, C. D., Cordeiro, R. T. & Bremec, C. S. (2016 a) Namuncura Marine Protected Area: an oceanic hot spot of benthic biodiversity at Burdwood bank, Argentina. Polar Biology, 39, 2373 - 2386. https: // doi. org / 10.1007 / s 00300 - 016 - 1913 - 2","Auscavitch, S. & Waller, R. (2017) Biogeographical patterns among deep sea megbenthic communities across the Drake Passage. Antarctic Science, 29 (6), 531 - 543. https: // doi. org / 10.1017 / S 0954102017000256","Schejter, L., Genzano, G., Gaitan, E., Perez, C. D. & Bremec, C. S. (2020) Benthic communities in the Southwest Atlantic Ocean: Conservation value of animal forests at the Burdwood bank slope. Aquatic Conservation: Marine and Freshwater Ecosystems, 30, 426 - 439. https: // doi. org / 10.1002 / aqc. 3265"]}

Desmophyllum dianthus (Esper, 1794) Material examined: BBB 2016: St. 18; St. 21. PD BB 2017: St. 10 (MACN-In: 41686, 41687, 41688, 41689, 41690). Distribution: Cosmopolitan. In the southern hemisphere it was recorded in Australia, New Zealand, Chile, Drake Passage and off South Georgias Islands (Cairns 1990), Atlantic Ocean reaching 42º S in deep waters (Cairns & Polonio 2013; Schejter et al. 2015). Remarks: Associations with other organisms are described in Schejter & Bremec (2019) and also, these authors recorded the species for the first time at MPA Namuncurá II. Family Flabellidae Bourne, 1905, Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on pages 217-218, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Cairns, S. D. (1990) Antarctic Scleractinia. In: Wagele, J. W. & Sieg, J. (Eds.), Synopses of the Antarctic benthos. Koeltz Scientific Books, Koenigstein, pp. 1 - 78.","Cairns, S. D. & Polonio, V. (2013) New records of deep-water Scleractinia off Argentina and the Falkland Islands. Zootaxa, 3691 (1), 58 - 86. https: // doi. org / 10.11646 / zootaxa. 3691.1.2","Schejter, L. & Bremec, C. S. (2019) Stony corals (Anthozoa Scleractinia) of Burdwood Bank and neighbouring areas, SW Atlantic Ocean. Scientia Marina, 83 (3), 247 - 260. https: // doi. org / 10.3989 / scimar. 04863.10 A"]}

Amphisbetia operculata (Linnaeus, 1758) Material examined: BBB 2016: St. 9; St. 12; St. 13; St. 27; St. 32; St. 33; St. 35. GARCÍA 2015: St. 14. (Fig. 2F) Distribution: Cosmopolitan. The species is widely reported in all southwestern Atlantic Ocean, from intertidal to 400 m depth (Blanco 1963 as Sertularia operculata; Oliveira et al. 2016; Genzano et al. 2017). Remarks: Big and mature clumps were found in all analyzed sites., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 212, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Blanco, O. M. (1963) Sobre algunos sertularidos de la Argentina. Notas del Museo de La Plata, 203, 163 - 180.","Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1","Genzano, G., Bremec, C. S., Diaz-Briz, L., Costello, J. H., Morandini, A. C., Miranda, T. P. & Marques, A. (2017) Faunal assemblages of intertidal hydroids (Hydrozoa, Cnidaria) from Argentinean Patagonia (Southwestern Atlantic Ocean). Latin American Journal of Aquatic Research, 45 (1), 177 - 187. https: // doi. org / 10.3856 / vol 45 - issue 1 - fulltext- 17"]}

Phelliactis cf. lophohelia Riemann-Zürneck, 1973 Material examined: BBB 2016: St. 21; St. 18. Remarks: If the specimens are lately confirmed as Phelliactis lophohelia, then it would be the first record of the species at the MPA Namuncurá II., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 216, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Riemann-Zurneck, K. (1973) Actiniaria des Sudwestatlantik I. Hormathiidae. Helgolander wissenschaftliche Meeresuntersuchungen, 25, 273 - 325. https: // doi. org / 10.1007 / BF 01611200"]}

Filellum sp. Material examined: BBB 2016: St. 23; St. 27; St. 28; St. 32; St. 40 (MACN-In: 43485). Remarks: Scarce colonies attached on hydroid colonies of Tulpa tulipifera, Halecium jaederholmi and Symplectoscyphus subdichotomus were found. Filellum antarcticum (Hartlaub, 1904) (Ritchie 1907 as Woea antarctica), Filellum serpens (Hassall, 1848) (Jäderholm 1905) and Filellum sp. (Vervoort 1972) were reported in Burdwood bank. However, identification to specific level is not possible due to the absence of reproductive structures in the examined material.

Grammaria abietina (M. Sars, 1851) Material examined: BBB 2016: St. 9; St. 11; St. 12; St. 27; St. 28; St. 32; St. 34; St. 35; St. 38; St. 39 (Fig. 2E) (MACN-In: 43437, 43438, 43439, 43440, 43441, 43442, 43443, 43444, 43445). Distribution: Boreal region of the Atlantic (Vervoort 1972). In the southwestern Atlantic Ocean, it was frequently reported in south Patagonian sector and subantarctic islands (50– 54°S) as Grammaria magellanica (see Blanco 1994; Oliveira et al. 2017). Remarks: Abundant, unfertile and big colonies were widely found in all analyzed areas. Usually, they were found growing on tubes of Chaetopterus antarcticus, a common tubicoulous polychaete found in several Patagonian areas (Bremec & Schejter 2019)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on pages 209-210, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Vervoort, W. (1972) Hydroids from the Theta, Vema and Yelcho cruises of the Lamont Doherty Geological Observatory. Zoologische Verhandelingen, 120, 1 - 47.","Blanco, O. (1994) Enumeracion sistematica y distribucion geografica preliminar de los Hydroides de la Republica Argentina. Suborden Athecata (Gymnoblastea, Anthomedusae), Thecata (Calyptoblastea, Leptomedusae) y Limnomedusae. Revista del Museo de La Plata, Nueva Serie, 14 (161), 181 - 216.","Schejter, L. & Bremec, C. S. (2019) Stony corals (Anthozoa Scleractinia) of Burdwood Bank and neighbouring areas, SW Atlantic Ocean. Scientia Marina, 83 (3), 247 - 260. https: // doi. org / 10.3989 / scimar. 04863.10 A"]}

Symplectoscyphus magellanicus (Marktanner-Turneretscher, 1890) Material examined: BBB 2016: St. 23. Distribution: The species was frequently reported in the Atlantic Ocean, Argentina, 36 – 56°S (Nutting 1904 as Sertularella magellanica; Hartlaub 1905 as Sertularella affinis; Vervoort 1972; Stepanjants 1979; Blanco 1984, 1994; Genzano & Zamponi 1997; Beshbeeshy & Jarms 2011; Miranda et al. 2015). It was reported also in Canal Pitt Chico, Chile (Galea 2007). Remarks: Scarce fragments of colonies were found detached from substrata. Symplectoscyphus milneanus (d’Orbigny, 1839) Material examined: BBB 2016: St. 4; St. 9. Distribution: South America. In the southwestern Atlantic the species is distributed, from 41°S to 56°S and at Malvinas / Falkland Islands reported as Sertularia milneana; Sertularella milneana, Sertularella plana; Sertularella meridionalis; Symplectoscyphus subarticulatus; and South Chile, near Isla Hanover (see Oliveira et al. 2016 and references therein). Remarks: Scarce fragments of colonies were found detached from substrata., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on pages 211-212, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Nutting, C. C. (1904) American hydroids. Part II. The Sertularidae. Special Bulletin of the United States National Museum, 4 (2), 1 - 325.","Hartlaub, C. (1905) Die Hydroiden der Magalhaensischen Region und chilenischen Kuste. In: Fauna chilensis. Zoologische Jahrbucher, Supplement 6 (3), 497 - 714.","Vervoort, W. (1972) Hydroids from the Theta, Vema and Yelcho cruises of the Lamont Doherty Geological Observatory. Zoologische Verhandelingen, 120, 1 - 47.","Stepanjants, S. (1979) Hydroids of the Antarctic and Subantarctic Waters. Biological Results of the Soviet Antarctic Expedition, 6, 1 - 199.","Blanco, O. M. (1984) Contribucion al conocimiento de hidrozoos antarticos y subantarticos. Contribucion del Instituto Antartico Argentino, 294, 1 - 53.","Blanco, O. (1994) Enumeracion sistematica y distribucion geografica preliminar de los Hydroides de la Republica Argentina. Suborden Athecata (Gymnoblastea, Anthomedusae), Thecata (Calyptoblastea, Leptomedusae) y Limnomedusae. Revista del Museo de La Plata, Nueva Serie, 14 (161), 181 - 216.","Genzano, G. N. & Zamponi, M. O. (1997) Frequency of study and diversity of benthic hydrozoa of the argentine continental shelf. Ciencias Marinas, 23 (3), 285 - 302. https: // doi. org / 10.7773 / cm. v 23 i 3.817","Beshbeeshy, M. & Jarms, G. (2011) Thekate Hydroiden von Patagonischen Schelf (Cnidaria, Hydrozoa, Thecata). Verhandlungen des Naturwischenschaftlichen Vereins in Hamburg, 46, 19 - 233.","Miranda, T. P., Genzano, G. N. & Marques, A. C. (2015) Areas of endemism in the Southwestern Atlantic Ocean based on the distribution of benthic hydroids (Cnidaria: Hydrozoa). Zootaxa, 4033 (4), 484 - 506. https: // doi. org / 10.11646 / zootaxa. 4033.4.2","Galea, H. (2007) Hydroids and hydromedusae (Cnidaria, Hydrozoa) from the fjords region of southern Chile. Zootaxa, 1597 (1), 1 - 116. https: // doi. org / 10.11646 / zootaxa. 1597.1.1","Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Actinauge longicornis (Verrill, 1882) Material examined: BBB 2016: St. 18. Distribution: The species was described by Verrill (1882) at the United States (39º93’N, 69º37’W, 380 m) and subsequently recorded by Carlgren (1942) in 39ºN, 35º30’W, in Bahamas (24ºN, 76º50’W, 73 m) by McMurrich (1898), and the Caribbean Sea (13º13’N, 61º 09’W, 236 m) by Verrill (1883). Riemann-Zürneck (1973) recorded the species near Río de la Plata frontal region and adjacent areas (33º43’– 38º06’S, 51º02’– 55º19’W). It was recorded from 125 m to 1000 m depth. This is the first record for the species at MPA Namuncurá II., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 216, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Verrill, A. E. (1882) Notice of the remarkable marine fauna occupying the outer banks off the southern coast of New England, 4. American Journal of Science, 23 (3), 216 - 225.","Carlgren, O. (1942) Actiniaria Part II. Danish Ingolf-Expedition, 5 (12), 1 - 92.","Verrill, A. E. (1883) Reports on the Anthozoa, and on some additional species dredged by the \" Blake \" in 1877 - 1879, and by the U. S. Fish Commission Steamer \" Fish Hawk \" in 1880 - 82. Bulletin of the Museum of Comparative Zoology, 11 (1), 1 - 72.","Riemann-Zurneck, K. (1973) Actiniaria des Sudwestatlantik I. Hormathiidae. Helgolander wissenschaftliche Meeresuntersuchungen, 25, 273 - 325. https: // doi. org / 10.1007 / BF 01611200"]}

Sertularella antarctica Hartlaub, 1900 Material examined: BBB 2016: St. 13; St. 32; St. 39. Distribution: Kerguelen, Indian Ocean; Cumberland Bay, South Georgia, South Atlantic Ocean (Vervoort 1972). In the southwestern Atlantic the species is distributed between 48°S to 56°S reported in Malvinas / Falkland Islands as Sertularella allmani (see Oliveira et al. 2016). Remarks: Scarce fragments of colonies were found detached from substrata., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 212, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Vervoort, W. (1972) Hydroids from the Theta, Vema and Yelcho cruises of the Lamont Doherty Geological Observatory. Zoologische Verhandelingen, 120, 1 - 47.","Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Balticina africana (Studer, 1878) Material examined: BBB 2016: St. 13. PD BB 2017: St. 31 (MACN-In 43489). Distribution: Atlantic coast of Africa as Halipteris africana (459– 659 m) (Williams 1990); San Antonio Cape, Buenos Aires coast, 38°06 ìS 55°13 ìW as Balticina sp. (440– 480 m) (Castro 1990); deep waters of SWAtlantic Ocean, Burdwood bank as Halipteris africana (641–701 m) (see Schejter et al. 2018). Remarks: Synonyms at the area: Balticina sp. (Castro 1990); Halipteris sp. (Schejter et al. 2018, p. 294); Halipteris heptazooidea Acuña & Zamponi, 1992 and Halipteris africana (Studer, 1878) (see Schejter et al. 2018, p. 297–298). One specimen of B. africana (St. 13) presented the sea anemone Hormathia pectinata fixed over the naked axis at the top end of the colony (Schejter et al. 2018)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 226, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Williams, G. C. (1990) A new genus of dimorphic soft coral from the south-western fringe of the Indo-Pacific (Octocorallia: Alcyoniidae). Journal of Zoology London, 221, 21 - 35. https: // doi. org / 10.1111 / j. 1469 - 7998.1990. tb 03772. x","Castro, C. B. (1990) Revisao dos Octocorallia (Cnidaria, Anthozoa) do litoral Sul-Americano: da foz do Rio Amazonas a foz do Rio da Prata. PhD Thesis, Universidade de Sao Paulo, Sao Paulo, 343 pp.","Schejter, L., Acuna, F. H., Garese, A., Cordeiro, R. & Perez, C. D. (2018) Sea pens (Cnidaria: Pennatulacea) from Argentine waters: new distributional records and first report of associated sea anemones. Pan-American Journal of Aquatic Sciences, 13 (4), 292 - 301.","Acuna, F. H. & Zamponi, M. O. (1992) Pennatulacea (Cnidaria: Octocorallia) de la region subantartica: nuevos taxa y registros. Iheringia, Serie Zoologia, 73, 47 - 53."]}

Plumularia setacea (Linnaeus, 1758) Material examined: BBB 2016: St. 27. Distribution: Cosmopolitan. Species widely distributed in the southwestern Atlantic, 20°S to 55°S (Oliveira et al. 2016). This is the first record in MPA Namuncurá I. Remarks: An immature colony was found detached from substrate. Synonyms at the area: Plumularia diploptera; Plumularia spiralis (see Oliveira et al. 2016)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 213, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Sertularella striata Stechow, 1923 Material examined: BBB 2016: St. 27 (MACN-In: 43482). Distribution: Species previously reported in South Atlantic, South Africa (Millard 1975) and Uruguay and Argentina, from 35 to 43°S (d’Orbigny 1839 as Sertularia patagonica; Nutting 1904 as Sertularella patagonica; Blanco 1967 as Sertularella atlantica; Blanco 1994). This study extends its distribution southwards (56°S) and represents the first record at MPA Namuncurá I. Remarks: Unfertile colonies were found. Synonyms at the area: Sertularia patagonica; Sertularella atlantica (see Oliveira et al. 2016)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 213, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Nutting, C. C. (1904) American hydroids. Part II. The Sertularidae. Special Bulletin of the United States National Museum, 4 (2), 1 - 325.","Blanco, O. M. (1967) Un nuevo aporte al conocimiento de la fauna hidroide argentina. Revista del Museo de La Plata, 10, 97 - 127.","Blanco, O. (1994) Enumeracion sistematica y distribucion geografica preliminar de los Hydroides de la Republica Argentina. Suborden Athecata (Gymnoblastea, Anthomedusae), Thecata (Calyptoblastea, Leptomedusae) y Limnomedusae. Revista del Museo de La Plata, Nueva Serie, 14 (161), 181 - 216.","Oliveira, O. M. P, Araujo, E. M., Ayon, P., Cedeno-Posso, C. M., Cepeda, A. A., Cordova, P., Galea, H. R., Genzano, G. N., Haddad, M. A., Mianzan, H. W., Migotto, A. E., Miranda, L. S., Miranda, T. P., Morandini, A. C., Nagata, R. M., Nascimento, K. B., Nogueira Jr., M., Palma, S., Quinones, J., Rodriguez, C. S., Scarabino, F., Schiariti, A., Stampar, S. N., Tronolone, V. B. & Marques, A. C. (2016) Census of the Cnidaria (Ceriantharia and Medusozoa) and Ctenophora from South American marine waters. Zootaxa, 4194 (1), 1 - 256. https: // doi. org / 10.11646 / zootaxa. 4194.1.1"]}

Javania cristata Cairns & Polonio 2013 Material examined: BBB 2016: St. 21 (MACN-In 41715). Distribution: Continental slope off central Argentina and Burdwood bank (Cairns 1982; Cairns & Polonio 2013). Remarks: This species was synonymized with J. cailleti (see Cairns & Polonio 2013; Schejter & Bremec 2019)., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on page 218, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Cairns, S. D. & Polonio, V. (2013) New records of deep-water Scleractinia off Argentina and the Falkland Islands. Zootaxa, 3691 (1), 58 - 86. https: // doi. org / 10.11646 / zootaxa. 3691.1.2","Cairns, S. D. (1982) Antarctic and Subantarctic Scleractinia. Biology of the Antarctic Seas XI. Antarctic Researsch Series, 34, 1 - 74. https: // doi. org / 10.1029 / AR 034 p 0001","Schejter, L. & Bremec, C. S. (2019) Stony corals (Anthozoa Scleractinia) of Burdwood Bank and neighbouring areas, SW Atlantic Ocean. Scientia Marina, 83 (3), 247 - 260. https: // doi. org / 10.3989 / scimar. 04863.10 A"]}

Thouarella spp. Material examined: 37 specimens not identified from four diferente morphotypes. BBB 2016: St. 12; St. 13; St. 18; St. 21; St. 28; St. 32; St. 36; St. 38; St. 40. PD BB 17: St. 9; St. 10; St. 16; St. 21; St. 23; St. 27; St. 29; St. 30; St. 43. GARCÍA 15: St. 17; St. 17bis. Distribution: Thouarella is the most speciose genus within the Family Primnoidae, especially diversified in subantarctic waters, mostly in depths from 400 to 5850 m (Taylor et al. 2013). Thouarella spp. were one of the dominant group in the studied area and were recorded at almost all stations (Schejter et al. 2020). Remarks: At least five species of Thouarella were already found in the Burdwood bank area: T. antarctica (Valenciennes, 1846), T. brucei Thomson & Ritchie, 1906, T. striata Kükenthal, 1907, T. chilensis Kükenthal, 1908, T. viridis Zapata-Guardiola & López-González, 2010 (Taylor et al. 2013); and one is first reported herein: T. variabilis Wright & Studer, 1889. Two potentially new species were identified from the Marine Protected Areas Namuncurá I and II, which did not fit in any species described so far. There are at least 38 valid Thouarella species (Núñez-Flores et al. 2020); however, as morphological plasticity is common among species of Thouarella, such as in T. variabilis Wright & Studer, 1889, further assessments (Scanning Electron Micrographies and COI, MutS sequencing) are needed in order to confirm if they are new species and identify at species level the four morphotypes analysed. This fact reinforces the still poorly known octocoral diversity in the region, despite several studies on that fauna., Published as part of Schejter, L., Genzano, G., Pérez, C. D., Acuña, F., Cordeiro, R. T. S., Silva, R. A., Garese, A. & Bremec, C. S., 2020, Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54 ºS- 56 ºS), pp. 201-239 in Zootaxa 4878 (2) on pages 225-226, DOI: 10.11646/zootaxa.4878.2.1, http://zenodo.org/record/4424884, {"references":["Taylor, M. L., Cairns, S. D., Agnew, D. & Rogers, A. D. (2013) A revision of the genus Thouarella Gray, 1870 (Octocorallia: Primnoidae), including an illustrated dichotomous key, a new species description, and comments on Plumarella Gray, 1870 and Dasystenella, Versluys, 1906. Zootaxa, 3602 (1), 1 - 105. https: // doi. org / 10.11646 / zootaxa. 3602.1.1","Schejter, L., Genzano, G., Gaitan, E., Perez, C. D. & Bremec, C. S. (2020) Benthic communities in the Southwest Atlantic Ocean: Conservation value of animal forests at the Burdwood bank slope. Aquatic Conservation: Marine and Freshwater Ecosystems, 30, 426 - 439. https: // doi. org / 10.1002 / aqc. 3265","Thomson, J. A. & Ritchie, J. (1906) The Alcyonarians of the Scottish National Antarctic Expedition. Transactions of the Royal Society of Edinburgh, 41 (3), 851 - 860.","Wright, E. P. & Studer, T. (1889) Report onthe Alcyonaria collected by H. M. S. Challenger during the years 1873 - 1876. Report on the Scientific Results of the voyage of H. M. S. Challenger, Zoology, 31, 1 - 314.","Nunez-Flores, M., Gomez-Uchida, D. & Lopez-Gonzalez, P. J. (2020) Molecular and morphological data reveal three new species of Thouarella Gray, 1870 (Anthozoa: Octocorallia: Primnoidae) from the Southern Ocean. Marine Biodiversity, 50, 30. https: // doi. org / 10.1007 / s 12526 - 020 - 01053 - z"]}