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"Flabellum thouarsii Milne Edwards and Haime, 1848
Flabellum thouarsii Milne Edwards and Haime, 1848, p. 265, pi. 8, fig. 5.—Studer, 1878, p. 630.—Not F. thouarsii; Gravier, 1914b, pp. 125-128 (is F. impensum Squires, 1962).--Not F. thouarsii; Wells, 1958, p. 268 (is F. impensum Squires, 1962), and F. flexuosum, n. sp.—Squires, 1961, pp. 29-38, figs. 5, 14-19, 21, 23, 27; 1962b, pp. 14, 18; 1969, p. 18, pi. 6, map 4.—Keller, 1974, pp. 200-203, pi. 1, figs. 1-4, pi. 2, figs. 1-7, pi. 3, figs. 1-4, pi. 4, figs. 1-7.—Cairns, 1979, p. 206.
Flabellum thouarsi; Milne Edwards and Haime, 1857, pp. 89, 90.
Flabellum curvatom; Gardiner, 1939, pp. 327, 328, pi. 20, figs. 1, 2 (part: all stations but Discovery sta. 182, WS sta. 839).—Squires, 1961, p. 38 (part: Vema sta. 14-18); 1962a, pp. 1-11, figs. 1-3.
Description. Corallum ceratoid to flabellate, attached only in young stage. Pedicel short, about 2.5-3.2 mm in diameter and usually worn away in older specimens. Pedicel expanding into straight corallum with angle of lateral edges varying from 30° (ceratoid) to 90° (flabellate); inclination of lateral faces rarely exceeding 20°. Largest specimen examined 33 x 22 mm in CD and 34 mm tall; an average-size specimen, however, 21 x 14 mm in CD and 23 mm tall. Theca usually worn or encrusted with calcareous invertebrates and ploychaete sand tubes. Calice elliptical, with GCD/LCD ratios of 1.3-1.7; calicular profile arched. Septa hexamerally arranged in five cycles; however, only largest specimens with 96 septa. Most specimens with 20-22 major septa (S1-3) enclosing triads of septa, or 80-88 total septa. Ten or eleven S1,2 equal in size and reaching center of fossa, sometimes fusing with those on opposite side. Ten or eleven S3 smaller, 20-22 S4 one third to one fourth of size of S3, and S5 rudimentary. Septa not exsert; each larger septum having shallow, concave notch near calicular edge, but never dentate. Inner edges of larger septa straight to slightly sinuous and thickened deeper in fossa. Septal granulation coarse and irregular, granules sometimes arranged in rows parallel to septal edge. Fossa relatively shallow. Rudimentary columella formed by fusion of thickened inner edges of S1 and S2 and additional irregular extensions from these septa. Internal stereome present in older specimens.
Remarks. Judging from substrate of attachment and attached worm tubes, this species seems to inhabit bottoms composed of small pebbles and coarse sand. Squires (1962a) discusses planulation, size of larva, and lack of periodicity for this species. Specimens from the northern range seem to attain a larger size and are therefore more easily confused with F. curvatum.
Discussion. As Squires (1961, p. 31) implied, Gardiner (1939) was probably not aware of F. thouarsii; most of his records of F. curvatum are average- to large-size specimens of F. thouarsii from its characteristic depth range, and there is one record each of F. impensum and F. curvatum. Authors that have relied on Gardiner's identifications (e.g., Wells, 1958; Keller, 1974) have been misled. Although Squires (1961) differentiated F. thouarsii from F, curvatum, he included one suite of uncharacteristically large specimens of F. thouarsii as F. curvatum (Vema station 14-18). Furthermore, his paper on the larvae of F. curvatum (Squires, 1962a) is also based on large F. thouarsii. Keller (1974) recognized two forms of F.
thouarsii, one similar to Squires's (1961) F. thouarsii and the other similar to his F. curvatum. She did not agree with Squires's (1961) reasons for separating the two species and therefore synonymized them. Keller's specimens all seem to be typical F. thouarsii. Ironically, her next species account, which describes F. antarcticum, is typical F. curvatum. Comparisons of F. thouarsii to the closely related F. curvatum and F. areum are discussed with those species.
Material. Eltanin sta. 217 (1), USNM 45650; sta. 370 (22), USNM 45664; sta. 974 (232), USNM 45649; sta. 976 (184), USNM 47222; sta. 977 (309), USNM 45648. Edisto sta. 49 (1), USNM 45643; sta. 50 (1), USNM 47218. Vema sta. 14-6 (10), AMNH; sta. 14-16 (18), USNM 45654, and (13), AMNH; sta. 14-18 (1), USNM 45655; sta. 15-PD3 (6), AMNH; sta. 15-99 (14), USNM 47212, and (1), AMNH; sta. 15-102 (135), USNM 47220; sta. 15-103 (2), USNM 45651, and (3), AMNH; sta. 15-108 (6), USNM 47216, and
(6), AMNH; sta. 15-110 (15), USNM 47221, and (19), AMNH; sta. 16-39 (8), USNM 47214, and (100), AMNH; sta. 17-74 (19), USNM 45617, and (8), AMNH; sta. 17-76 (40), USNM 47211, and (81), AMNH; sta. 17-88 (10), USNM 45618, and (10), AMNH; sta. 17-89 (13), USNM 47217, and (21), AMNH; sta. 17-90 (1), AMNH; sta. 17-97 (100), AMNH; sta. 18-13 (32), USNM 47219; sta. 18-14 (3), USNM 47215; sta. 18-16 (4), USNM 47213. BR sta. 25149 (2), USNM 47210. Specimens (2) of Studer (1878), Museum fur Naturkunde, Berlin (number 1737); some Vema records first reported by Squires (1961, 1962a, b) as F. thouarsii and F. curvatum; some specimens identified as F. curvatum by Gardiner (1939): WS sta. 76 (1), BM 19184.108.40.206; sta. 216 (19), BM 19220.127.116.11- 264; sta. 244 (11), BM 1918.104.22.168-164; sta. 247 (1), BM 1922.214.171.124; sta. 792 (1), BM 19126.96.36.199 and Discovery sta. 652 (7), MCZ 3589. Syntypes.
Types. Milne Edwards and Haime's original description gave measurements for only one specimen, implying a holotype. However, at the Museum National d'Histoire Naturelle, Paris, there are four specimens labeled F. thouarsi from the ‘Îles Malouines’ in the Milne Edwards Collection, two numbered 1028 and two numbered 1029. Three are F. thouarsii; a fourth from lot 1029 appears to be an Indo-Pacific hermatype of similar shape. One of the specimens from lot 1028 has measurements similar to those of the specimen in the original description and may be the holotype. Gravier (1914b, pp. 127, 128) reported two types (syntypes ?) of F. thouarsii at the Museum National d'Histoire Naturelle and two additional specimens identified as this species, one from 'Îles Malouines’ and the other 'trouvé dans une éponge. ' This may explain the presence of four identified specimens of F. thouarsii but does not help in determining the type. Because of this uncertainty a lectotype is not chosen. Type-locality: Malouine Islands (Falkland Islands or Islas Malvinas).
Distribution. Off southeastern South America from Rio de la Plata, Uruguay, to Cape Horn; off Falkland Islands. Squires's (1969) record from the Scotia Ridge undocumented (Map 7). Depth range: 71-305 m." Cairns 1982, pp. 34-35, Plate 10, figs. 3-7.