Deltocyathus rotulus (Alcock, 1898)

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

Deltocyathus rotulus (Alcock, 1898)

Fig. 7E, F

Trochocyathus rotulus Alcock, 1898: 16, pl. 2, figs 1, 1A.

Deltocyathus fragilis Alcock, 1902a: 99, 100. - Alcock 1902c: 21, pl. 1, figs 15, 15A.

Deltocyathus rotulus . -van der Horst 1931: 6. -Gardiner and Waugh 1938: 196. - Yabe and Eguchi 1937: 129. -Keller 1982: 50. - Cairns and Keller 1993: 245, pl. 5, fig. I. -Cairns 1994: 55, 56, pl. 24, figs J, K. - Cairns and Zibrowius 1997: 125, 126, fig. 16A-C. - Cairns 1999a: 91-92. -Cairns 2004a: 280. -Kitahara and Cairns 2009: 238, fig. 1B. - Kitahara and Cairns 2021: 399, 401, figs 204, 216A-D.

Type locality.

North of Maldive Atoll, Flores Seas (HMS ‘Investigator’ stn. 216: 7°24'S, 118°15.2'E); 794 m ( Alcock 1898; Kitahara and Cairns 2009).

Type material.

The holotype is presumed to be deposited at the IM (Cairns 2004a; Kitahara and Cairns 2009).

Material examined.

USNM 91550 (1 specimen): Eastern margin, 28 km from Scottburgh/ 21 km off Mkomazi, 30°11'59.99"S, 32°01'00.00"E; 1360 m.

Description.

Corallum discoidal, unattached, with a flat to slightly bowl-shaped base. Calice slightly elliptical (GCD:LCD = 1.2), with a lanceted and scalloped calicular margin. Specimen examined 30.4 × 25.5 mm in CD. All costae serrated and prominent at calicular margin. Intercostal spaces deep and wider at calicular margin, becoming progressively narrower towards base. Costae granular, resulting in a serrated costal margin. Corallum white, being light reddish brown around columella.

Septa hexamerally arranged in five cycles according to the formula: S1-2 > S3 > S4 > S5 (total of 96 septa). S1-2 appearing independent septa, but fusing to neighbouring septa through porous connections. S1-2 moderately exsert, bear pali, each of which is separated from its septum by a notch. S3 ¾ the width of S1-2, less exsert, and sometimes each bearing a small palus. S4 less wide than S3, but equally exsert, and each bearing a tall palus, which form a distinctive crown around columella. S5 rudimentary. All septa fuse to adjacent septa, but position of fusion varies: S1-4 join neighbouring septa near columella whilst S5 join S4 near calicular margin. P1-3 small, with P1-2 being ¼ or ½ the size of P4, and P3 consistently half the size of P1-2, positioned at porous fusions. P4 positioned further away from columella, alluding to a crown of 24 pali. Upper margins of all septa smooth. Fossa shallow, containing a papillose columella composed of irregularly shaped papillae.

Distribution.

Regional: Eastern margin of South Africa, off Scottburgh; 1360 m. Elsewhere: Mozambique; Zanzibar ( Cairns and Keller 1993); Maldives ( Alcock 1898; Gardiner and Waugh 1938); Gulf of Aden (Gardiner and Waugh 1938); Sri Lanka (van der Horst 1931); Tanzania (Gardiner and Waugh 1938); Japan (Cairns 1994); Philippines; Indonesia; Malaysia ( Alcock 1902c; Cairns and Zibrowius 1997); Vanuatu; Wallis, and Futuna region ( Cairns 1999a); Australia (Cairns 2004a); New Caledonia (Kitahara and Cairns 2009, 2021); 210-2340 m.

Remarks.

Among the Deltocyathus s from South Africa, the Indo-Pacific D. rotulus differs from the Atlantic D. italicus in having a large and discodial corallum, a total of five cycles of septa (the highest cycle sometimes incomplete), costae giving a serrated appearance, and the reddish brown pigmentation around the columella.

Figures

Figure 7. A, D Vaughanella concinna A, B (MN _ SM 134, off Port Edward, 900 m) A calicular view B lateral view C, D (SAMC _ A 072973, locality data unknown, 517 m) C calicular view D lateral view E, F Deltocyathus rotulus (USNM 91550, off Scottburgh, 1360 m) E calicular view F lateral view G, H Atlantia denticulata sp. nov. (SAMC _ A 090157, off Gouritsmond, 170 m) G close-up of corallites H full view I, J Balanophyllia (Balanophyllia) bonaespei (USNM 1423303, off the Agulhas, 32 m) I calicular view J lateral view K, N Balanophyllia (Balanophyllia) capensis K, M (SAM _ H 3048, off Cape Point, depth unknown) calicular view L, N (BMNH _ 1939.7.20.479 - 500, locality data unknown) lateral view O, P Balanophyllia (Balanophyllia) diademata (SAMC _ A 073016, off Richards Bay, 500 m) O calicular view P Lateral view. Scale bars: 10 mm (A-H, K-P); 100 mm (I, J).