Flabellum (Ulocyathus) alabastrum Moseley, 1873

Filander, Zoleka N., Kitahara, Marcelo V., Cairns, Stephen D., Sink, Kerry J. & Lombard, Amanda T., 2021, Azooxanthellate Scleractinia (Cnidaria, Anthozoa) from South Africa, ZooKeys 1066, pp. 1-198 : 1

Flabellum (Ulocyathus) alabastrum Moseley, 1873

Fig. 11K, L.

Flabellum alabastrum Moseley in Thompson, 1873: 403, fig. 2. - Moseley 1881: 169, pl. 7, figs 1, 1A, B, 2, 2A, B, pl. 16, fig. 11. - Zibrowius 1980: 148, pl. 77 A-J. - Cairns 1981: 6. -Zibrowius 1985: 318. - Zibrowius and Gili 1990: 38. pl. 2S, T.

Flabellum minus Duncan 1878: 243, pl. 45, figs 10-13.

Flabellum (Ulocyathus) alabastrum . -Cairns 1989: 54.

Type locality.

Azores (HMS ‘Challenger’ stn. 73: 37°26'00"N, 25°13'00"W); 1829 m ( Zibrowius 1980).

Type material.

Syntypes are deposited at the BMNH ( Zibrowius 1980).

Material examined.

SAMC_A090102 (1 specimen): Southern margin, 125 km from Agulhas/ 134 km off Ratels Estuary, 35°56'37.38"S, 20°02'27.30"E; 168 m.

Description.

Corallum unattached with a narrow and circular pedicel. Calice compressed (GCD:LCD = 1.4), with a highly jagged calicular margin. Largest specimen examined 28.3 × 19.8 mm in CD, 22.1 mm in H, and 2.2 mm in PD. Thecal faces planar and diverging at an angle of 110°. Thecal edges crested and diverging in an angle of 150° (excluding crests). Thecal crest sinuous. C1-3 well developed and extending from calicular margin towards base. Thin and faint growth ridges, corresponding to higher cycle septa (S4-5) present. Corallum predominantly white, but pedicel and intercostal striae reddish brown.

Septa arranged in five cycles, last being incomplete, according to the formula: S1-3> S4> S5 (≤ 80 septa). S1-3 equidistant and join columella with moderately sinuous axial margins. S4 ~ ½ the size of S1-3, and bear sinuous axial margin. S5 rudimentary. Septal faces bear small spines sparsely arranged along the septal margins. Fossa moderately deep, narrow, and containing a rudimentary columella composed by fusion of lower axial margin of larger septa.

Distribution.

Regional: Western to southern margin of South Africa, off Alexander Bay extending towards Algulhas; 168-1089 m. Elsewhere: Walvis Ridge ( Zibrowius and Gili 1990); Hebrides; Azores; Gulf of Guinea, Georgia towards Davis Strait ( Cairns 1981); Bahamas ( Zibrowius 1980); 357-2000 m.

Remarks.

Flabellum (U.) alabastrum is one of the four flabellid species with a constricted corallum and may be mistaken with F. lowekeyesi Squires & Ralph, 1965. However, the two species differ in having a shorter, crested lateral edges (LEL: H = 0.3-0.5 vs. 0.9 for F. alabastrum ), and a taller corallum (GCD: H = 1.0-1.3 vs. 1.5 for F. alabastrum )( Cairns 1989a, 1995). Flabellum (U.) alabastrum is historically only known from the Atlantic, thus the current South African record extends the species distribution to the Indian Ocean (east of Cape Point). Furthermore, the examined specimens confirm that the F. alabastrum is found 189 m shallower than previously known.

Figures

Figure 11. A Tubastraea sp. cf. Tubastraea diaphana (SAM _ H 5103, Cape Vidal, 59 m) A lateral view B Tubastraea micranthus (ORI _ EIb 3, locality data unknown) B full view C, D Flabellum (Flabellum) leptoconus (ORI _ DIIa 1, Port St. Johns, 409 - 440 m) C calicular view D lateral view E, H Flabellum (Flabellum) pavoninum E, F (SAMC _ A 073135, off Coffee Bay, 250 - 280 m) E calicular view F lateral view G, H (SAM _ H 4582, off Shaka's Rock, 150 m) G calicular view H lateral view I, J Flabellum (Flabellum) politum (SAMC _ A 090160, off Shaka's Rock, 53 - 57 m) I calicular view J lateral view K, L Flabellum (Ulocyathus) alabastrum (SAMC _ A 090102, off the Agulhas, 168 m) K calicular view L lateral view M, N Flabellum (Ulocyathus) lowekeyesi (SAM _ H 1695, off Kosi Bay Estuary, 720 - 780 m) M calicular view N lateral view O, P Javania antarctica (SAMC _ A 090150, off Gouritsmond, 333 m) O calicular view P lateral view. Scale bars: 10 mm.