Rhizotrochus typus Milne-Edwards & Haime, 1848

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

Rhizotrochus typus Milne-Edwards & Haime, 1848

Fig. 12E-H

Rhizotrochus typus Milne-Edwards & Haime, 1848a 282, pl. 8, fig. 16. - Pourtalès 1871: 13. - Studer 1881: 28. - Moseley 1881: 131. -von Marenzeller 1907: 23, pl. 2, fig. 5. - Yabe and Sugiyama 1936: 346-348, figs 3, 3A. - Cairns 1989a: 79-81, pl. 41, figs F, J. -Cairns 1994 81, pl. 35, figs A-C, pl. 40, figs H, I. - Cairns and Zibrowius 1997: 161, figs 22D, E. - Cairns 1999a: 127, fig. 22A. - Cairns et al. 1999: 31. -Tachikawa 2005: 10-11, pl. 4, figs E-H. - Cairns 2009: 21. - Kitahara and Cairns 2021: 234-236, figs 120F-G, 121.

Flabellum rubrum . -Gardiner 1902 a: 125-152, pl. 4, fig. 34. -Gardiner 1902 b: 464-471.

Flabellum harmeri . - Boshoff 1981: 35.

Monomyces sp. - Boshoff 1981: 35.

Type locality.

Singapore, depth unknown (Cairns 1994).

Type material.

Two syntypes are deposited at the MNHNP (Cairns 1994).

Material examined.

ORI_DIIb3 (in part: 1 specimen): Locality data unknown, 27 m . ORI_DIIc1 (4 specimens), SAMC_A072990 (1 specimen): Locality data unknown. SAMC_A073048 (1 specimen): Locality data unknown; SAMC_A073194 (2 specimens): Southern margin, 5 km from Gonubie / 3 km off Gqunube Estuary, 32°57'11.87"S, 28°02'48.12"E; 30 m . SAMC_A073247 (3 specimens): Eastern margin, 34 km from Coffee Bay / 7 km off Ntlonyane Estuary, 32°15'11.99"S, 28°57'41.99"E; 160 m . SAM_ A90094 (2 specimens): Eastern margin, 34 km from Coffee Bay / 16 km from Ntlonyane Estuary, 32°16'59.99"S, 29°03'59.99"E; 160 m . UCTES_SCD39B (3 specimens): Eastern margin, 34 km from Coffee Bay / 16 km from Ntlonyane Estuary, 32°16'59.99"S, 29°03'59.99"E; 160 m

Imagery data.

BMNH 1939.7.20.816-833 (1 specimen), BMNH 1950.1.10.34 (1 specimen), BMNH 1950.10.97-102 (1 specimen), BMNH 1950.1.11.63 (1 specimen): Cape of Good Hope, other locality data unknown.

Description.

Corallum conical, robust, and attached to substrate by a slender and non-reinforced pedicel (< 3 mm in D). Calice irregularly elliptical (GCD:LCD = 1.2-1.5), with thin, smooth, and flared calicular margin. Largest specimen examined (SAMC_A072990) 14.4 × 9.8 mm in CD, and 21.1 mm in H. Theca thin and usually encrusted, lower theca bears numerous (> 5) hollow rootlets that improve corallum anchoring (rootlets of examined specimens broken). Costae equally wide but poorly developed. Intercostal striae shallow. Transversal chevron-shaped growth lines present from calicular margin towards pedicel. Corallum predominantly white, becoming light-beige from lower theca towards base.

Septa hexamerally arranged in six cycles, last being incomplete, according to the formula: S1-2 > S3 > S4 > S5 > S6. However, specimens examined also have fifth cycle incomplete (totalling 78-89 septa). S1-2 equal in width and have straight and vertical axial margin, which become slightly sinuous deeper in the fossa. Higher cycle septa (S3-5) progressively smaller, and bearing slightly sinuous axial margins. S6 if present rudimentary, but, if absent, then S5 rudimentary. Septal faces finely granulated. Fossa deep, with rudimentary or absent columella.

Distribution.

Regional: Southern and eastern margin of South Africa, off Gonubie extending Coffee Bay; 30-160 m. Elsewhere: Andaman Islands; Bay of Bengal ( Alcock 1893); Red Sea (von Marenzeller 1907); Japan ( Cairns 1989b, 1994); South China Sea; Philippines; Indonesia ( Cairns and Zibrowius 1997); Vanuatu ( Cairns 1999a); New Caledonia ( Kitahara and Cairns 2021); 20-1048 m.

Remarks.

Although Rhizotrochus typus was collected off the South African margin (Cape of Good Hope) in the early 20th century, it was incorrectly identified by Gardiner (1902 a, 1902b) as Flabellum rubrum . Subsequently, Boshoff (1981) misidentified R. typus as two other flabellids ( F. harmeri [ORI_DIIb3] and Monomyces sp. [ORI_DIIc1]). Rhizotrochus has long been synonymiszed with Monomyces , however historical accounts have outlined the difference in the number and placement/pattern of their rootlets, in which Rhizotrochus has > 2 rootlets that are not fused to pedicel as compare with Monomyces Ehrenberg, 1834, which displays < 2 rootlets fused to the pedicel ( Cairns 1989a). Despite the examined specimens having broken rootlets (thus not showing whether they join pedicel or not), we herein provide the first reliable record for the species within South African localities by use of the number of rootlets (> 5) observed.

Figures

Figure 12. A, B Javania insignis (SAMC _ A 090116, off Port Dunford, 85 m) A calicular view B lateral view C, D Placotrochides scaphula (USNM 91772, off Scottburgh, 1360 m) C calicular view D calicular view E, H Rhizotrochus typus E, F (SAMC _ A 090094, off Coffee Bay, 160 m) E calicular view F lateral view G, H (SCD 39 B, off Coffee Bay, 160 m) G calicular view H lateral view I, J Truncatoflabellum formosum (SAM _ H 1389, off Shaka's Rock, 183 m) I calicular view J lateral view K, L Truncatoflabellum gardineri (SAM _ H 3847, off Shaka's Rock, 138 m) K calicular view L lateral view M, N Truncatoflabellum inconstans (SAM _ H 1241, off Kei Mouth, 66 m) M calicular view N lateral view O, P Truncatoflabellum multispinosum (SAMC _ A 087450, locality data unknown) O calicular view P lateral view. Scale bars: 10 mm.