Rhizosmilia robusta Cairns in Cairns & Keller, 1993

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

Rhizosmilia robusta Cairns in Cairns & Keller, 1993

Fig. 4N, O

Rhizosmilia robusta Cairns in Cairns & Keller, 1993: 250-253, pl. 6, figs F-I. - Cairns and Zibrowius 1997: 133-134. - Cairns 1999a: 107. - Cairns et al. 1999: 24. - Cairns 2009: 14. - Kitahara et al. 2010a 108, figs 88-89. - Kitahara et al. 2010b: 9. - Kitahara and Cairns 2021: 554-556, figs 305D-I, 306.

Type locality.

Off Inhaca Island, Mozambique (RV 'Anton Bruun’ stn. 373B: 26°00'00"S, 33°05'00"E); 135 m ( Cairns and Keller 1993).

Type material.

The holotype is deposited at the NMNH ( Cairns and Keller 1993).

Material examined.

USNM 91689 (3 specimens): Eastern margin, 42 km south of Ponta Do Ouro/ 27 km off Kosi Bay Estuary, 27°13'30.00"S, 32°49'30.00"E; 74 m.

Description.

Adapted from Cairns and Keller 1993: Colony phaceloid. Corallites trochoid, firmly attached through a massive pedicle (PD:GCD = 0.03), that expands into a thin encrusting base. Lower pedicel reinforced by concentric rings of hollow chambers. Calice elliptical (GCD:LCD = 1.18), with a jagged calicular margin. Holotype (USNM 91681) 31 × 26.20 mm in CD, 16.80 mm in PD, and 25 mm in H. Costae equal and bearing low and rounded granules. Intercostal striae shallow. Corallum white.

Septa arranged in five cycles according to the formula: S1 > S2 > S3 > S4 > S5. S1 moderately exsert, and extend to columella with vertical to straight axial margins. Higher cycle septa (S2-5) progressively less exsert and less wide, except for those S5 adjacent to S1 which are more exsert than S4. Axial margins of S2 also straight, but those of S3-4 slightly sinuous. S5 rudimentary and irregular in profile (i.e., may be straight to slightly sinuous or sinuous to dentate). All septal faces smooth, bearing only sparsely spaced low-profile granules. Small pali present before penultimate cycle, usually indistinguishable from columellar elements. Fossa deep and bearing endothecal dissepiments. Columella trabecular, composed of an irregular group of intertwined elements.

Distribution.

Regional: Eastern margin of South Africa, off Kosi Bay Estuary (41 km south of Ponta Do Ouro: Mozambique); 75 m. Elsewhere: Mozambique; Madagascar ( Cairns and Keller 1993); Philippines ( Cairns and Zibrowius 1997); New Caledonia ( Kitahara and Cairns 2021); 66-996 m.

Remarks.

As no new samples have been examined, the description above is adapted from Cairns and Keller (1993), who noted that although the holotype is a phaceloid colony with four corallites, paratypes (specimen examined and imaged herein) represent individual corallites that were broken apart from a larger colony or have not yet formed a colony. Variation in septal cycles correlates to corallum size: the fourth septal cycle is complete at a GCD between 8 and 9 mm, whereas the fifth is completed when the corallite is > 19-21 mm in GCD. The largest corallite (Philippines, see Cairns and Zibrowius 1997 [page 134]), measures 29.8 × 36.7 mm in CD, 18.1 mm in PD, 41.6 mm in H, have eight pairs of S6, and one pair of S7 (total of 116 septa). Notable differences between Rhizosmilia robusta from the Pacific and southwestern Indian Ocean are the position of paliform lobes, which are present before the penultimate cycle (P4, if S5 is present; and P3 if S5 is absent) in the latter and occur before S4 (irrespective of the presence of S6-7) in the former. This is the only representative of the genus in South African waters.

Figures

Figure 4. A, B Heterocyathus alternatus (ORI _ DIIIe 1 _ 1, locality data unknown) A calicular view B lateral view C, D Heterocyathus monileseptatum sp. nov. (SAM _ H 1431, off Durban Harbour, 99 m) C calicular view D lateral view E, F Heterocyathus sulcatus (SAMC _ A 073123, off Shaka's Rock, 100 - 105 m) E calicular view F lateral view G, H Labyrinthocyathus delicatus (SAM _ H 2836, off East London, 146 - 238 m) G calicular view H lateral view I, K Monohedotrochus capensis comb. nov. I, J (SAMC _ A 088924, off Kidds Beach, 247 - 147 m) I calicular view J lateral view K (SAM _ H 3210, off Scottburgh, 690 m) calicular view L, M Polycyathus sp. (USNM 91677, off Port Dunford, 69 m) L calicular view M full view N, O Rhizosmilia robusta (USNM 91689, off Kosi Bay Estuary, 74 m) N calicular view O lateral view P Solenosmilia variabilis (SAM _ H 3158, off Cintsa, 630 m) P full view. Scale bars: 10 mm (A-G, I-O); 100 mm (H, P).