Sphenotrochus (Sphenotrochus) evexicostatus 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

Sphenotrochus (Sphenotrochus) evexicostatus Cairns in Cairns & Keller, 1993

Fig. 15K, L

Sphenotrochus intermedius . - Macnae and Kalk 1958: 123.

Sphenotrochus sp. -Pichon 1974: 176, fig. 5.

Sphenotrochus aurantiacus . - Boshoff 1981: 38-39 (in part).

Sphenotrochus (Sphenotrochus) evexicostatus Cairns in Cairns & Keller, 1993: 255, 258, fig. 9A-H.

Type locality.

Off south-eastern Mozambique (RV 'Anton Bruun’ stn. 372B: 24°48'00"S, 34°59'00"E); 42 m ( Cairns and Keller 1993).

Type material.

The holotype and five paratypes are deposited at the NMNH, whilst one paratype is deposited at the SAM ( Cairns and Keller 1993).

Material examined.

ORI_DIIIi1 (3 specimens): Locality data unknown. SAMC_A090080 (3 specimens): Southern margin, 22 km from Cape Point / 4 km off Elsies Estuary, 34°09'59.99"S, 18°27'29.99"E; 24 m. SAMC_A090083 (1 specimen): Southern margin, 18 km from Cape Point / 16 km off Buffels Wes Estuary, 34°13'00.00"S, 18°35'00.0"E; 44 m. SAMC_A090085 (in part: 1 specimen): Locality data unknown; 43 m. SAM_H806 (8 specimens): Southern margin, 37 km from Port Elizabeth / 32 km off Bakens River Estuary, 34°05'29.99"S, 25°55'14.99"E; 20 m. SAM_H3200 (2 specimens): Eastern margin, 19 km from Shaka’s Rock / 3 km off Mdloti Estuary, 29°38'59.99"S, 31°07'59.99"E; 49 m. SAM_H3201 (1 specimen): Eastern margin, 19 km from Shaka’s Rock / 3 km off Mdloti Estuary, 29°38'59.99"S, 31°07'59.99"E; 71- 73 m. SAM_H3202 (10 specimens): Southern margin, 18 km from Gonubie /off Gqunube Estuary, 29°38'59.99"S, 31°07'59.99"E; 90 m. SAM_H4584 (1 paratype): Eastern margin, 31 km south of Ponta Do Ouro / 32 km off Kosi-Kumpungwini (Sifungwe) Estuary, 24°48'00"S, 34°59.00"E; 42 m. USNM 77188 (12 paratypes): Eastern margin, 24 km from Shaka’s Rock / 5 km off Mdlotane Estuary, 29°18'59.99"S, 31°21'00.00"E; 38 m.

Description.

Corallum cuneiform. Thecal faces diverge at 12°, producing a triangular profile in lateral view. Base rounded. Calice elliptical (GCD:LCD = 2.4-3.1), with serrated calicular margin. Largest specimen examined (SAM_H806) 6.7 × 2.3 mm in CD, and 8.8 mm in H, showing an episode of rejuvenescence. Costae rounded, equal in width, and do not overlap with adjacent costae. Costae slanting inwards towards base, being continuous until ~ 1.5 mm above base where they form discontinuous ridges. All costae smooth, except C1 and adjacent C4, which are slightly granulated. Pairs of C4 occur in each half-system adjacent to S1 (32 costae), but S4 do not correspond to C4. Intercostal striae wider than costae. Corallum white but sometimes light-yellow to brown.

Septa hexamerally arranged in three cycles according to the formula: S1-2 > S3 (24 septa). S1-2 moderately exsert, equal in width, and join columella deep in fossa with slightly sinuous axial margin. S3 less exsert, 1/3 the width of S1-2, and bear slightly dentated axial margin. Columella solid and lamellar. Lamella rises almost to the height of septal upper margins. Columellar elements and septal faces bear low-profile granules.

Distribution.

Regional: Southern to eastern margin of South Africa, from off Cape Point extending towards Durban; 24-90 m. Elsewhere: Mozambique ( Cairns and Keller 1993); Madagascar (?) Pichon 1974); 12-73 m.

Remarks.

Examined specimens of Sphenotrochus (S.) evexicostatus add no taxonomic knowledge to the existing diagnosis. The species is well described by Cairns and Keller (1993), who noted that it may co-exist with S. imbricaticostatus , which has similar septa, costae, and columella. However, S. evexicostatus can be distinguished in having: round, ridged, non-imbricate, equidistant costae; wide intercostal striae that are > 35% width of costae; and S3 ~ 1/3 the width of S1-2. The ornamentation of costae of S. evexicostatus , which is continuous from calice and become disconnected ~ 1.5 mm from base, is also a distinctive feature.

Figures

Figure 15. A, B Cyathotrochus pileus (SAMC _ A 087424, off Durban, 270 m) A calicular view B lateral view C, D Deltocyathoides orientalis (BIVa 2, locality unknown, 80) C calicular view D basal view E, F Deltocyathoides sentus (USNM 91551, off Shaka's Rock, 300 m) G, H Sphenotrochus (Eusthenotrochus) gilchristi (SAMC _ A 090086, off Cape Point, 24 m) G calicular view H lateral view I, J Sphenotrochus (Sphenotrochus) aurantiacus (SAM _ H 1416, off the Agulhas, 366 m) I calicular view J lateral view K, L Sphenotrochus (Sphenotrochus) evexicostatus (SAMC _ A 090085, locality data unknown, 43 m) K calicular view L lateral view M, N Sphenotrochus (Sphenotrochus) imbricaticostatus (USNM 91715 _ Holotype, off Kosi-Kumpungwini (Sifungwe) Estuary, 44 m) K calicular view L lateral view O, P Tropidocyathus lessonii (SAMC _ A 073218, off Kosi Bay Estuary, 74 m) O calicular view P lateral view. Scale bars: 10 mm (A-H, J-M, O-P); 2 mm (I, N).