Trochocyathus wellsi, Cairns, 2004

Cairns, S. D., 2004, The Azooxanthellate Scleractinia (Coelenterata: Anthozoa) of Australia, Records of the Australian Museum 56, pp. 259-329 : 288

Trochocyathus wellsi n.sp.

Figs. 5A,B

Not Trochocyathus virgatus Alcock, 1902a: 98–99 .

Trochocyathus virgatus .– Wells, 1964: 112–113, pl. 1, figs. 8–10 (Qld).– Veron, 1986: 606 (listed).

Records/Types. Holotype: Kimbla-1, AM G16704 . Paratypes: Kimbla-1, 17, AM G16335; “about 14 miles (= 22.4 km) due east of Jumpin Pin (27°45'S.)”, 86 m, 2 paratypes , USNM 68373 ( Wells, 1964: 113). Type Locality: 27°31'S 153°40'E (off Moreton Island ), 75–81 m.

Description. Corallum ceratoid, attached through a slender (PD:GCD = 0.32–0.49), elongate pedicel and a thin encrusting base. Holotype 7.8× 6.8 mm in CD and 14.7 mm in height, having a PD of 3.6 mm. Upper part of corallum slightly flared; calice elliptical (GCD:LCD = 1.09–1.21). Calicular margin lancetted, each pair of CS4 adjacent to the 6 CS1 forming a rectangular projection on the calicular margin, a smaller lancet corresponding to the CS2 and their adjacent CS4. Costal granules on lower half of corallum low but arranged in faint transverse rows, whereas granules on upper half of corallum arranged on longitudinally oriented costae. Edge zone narrow, extending only about 2.5 mm from calicular edge, below which many kinds of encrusting organisms attach to the corallum, e.g., hydroids, foraminifera, serpulids, sponges, bryozoans, and small bivalves. Corallum uniformly white.

Septa hexamerally arranged in 4 cycles according to the formula: S1>S2>S4>S3, but few coralla have the full complement of 48 septa and there is no direct relationship between GCD and number of septa. For example, one of the smallest coralla (GCD= 5.5 mm) has 48 septa, whereas the largest corallum (GCD= 8.8 mm) has only 40 septa; the holotype has 42 septa. S1 are highly exsert (1.7–2.1 mm), have straight to only slightly sinuous axial edges, and in old specimens can be quite thick. S2 less exsert (about 1.2 mm) and about 80% the width of an S1. S3 about 0.4 mm exsert but dimorphic in width, those S3 flanked by S4 being the smallest of the septa (about 65% width of an S1), but those S3 unflanked by S4 being almost as wide as an S1. S4 also dimorphic in width, those adjacent to an S1 being slightly wider than the S3 they flank, those adjacent to an S2 being equal to or only slightly wider than the adjacent S3. A lamellar palus about 0.4 mm in width occurs before each S3 and is aligned with that septum; occasionally a second P3 occurs slightly closer to the columella. P1 and P2 are less distinctive, shaped as a papilla circular in cross section and about 0.2 mm in diameter, which is aligned with the axial edge of each S1, but P2 are difficult to distinguish. Fossa of moderate depth, containing a papillose columella of 6–10 spiny elements indistinguishable from the P1.

Remarks. Trochocyathus wellsi is easily distinguished from Tethocyathus virgatus by its lack of epitheca, white corallum, lancetted calicular edge, and its smaller corallum size and ceratoid shape. It also differs in its poorly defined palar ring structure, which distinguishes it from all other species of Trochocyathus and may be justification for ultimately placing it in a different genus.

Etymology. Named in honour of John W. Wells, who first examined this species and who significantly added to our knowledge of deep-water Australian corals ( Wells, 1958, 1964).

Distribution. Known only from the region off Brisbane, Queensland, 75– 86 m.