Lissotrochus curvatus, Cairns, 2004

Cairns, S. D., 2004, The Azooxanthellate Scleractinia (Coelenterata: Anthozoa) of Australia, Records of the Australian Museum 56, pp. 259-329 : 298

Lissotrochus curvatus n.sp.

Figs. 8F–K

Records/Types. Holotype: Franklin 03/99/D11, AM G16745 . Paratypes: Franklin 03/99/D10, 25, USNM 1008843 ; Franklin 03/99/D11, 116: 108 (including SEM 1008 and 1009), USNM 1008844 , 3 , WAM Z20517, and 5, ZMUZ; Franklin 03/99/D12, 10, USNM 1008845 ; Franklin

03/99/D13, 4, USNM 1008846 . Type Locality: 20°14.49'S 151°47.53'E ( Marion Plateau , Queensland), 342 m.

Description. Corallum ceratoid, cornute (usually curved about 45° in plane of GCD), and free, the base pointed and about 0.30–0.45 mm in diameter. Largest corallum 3.25× 2.95 mm in CD and 9.7 mm in height, the holotype being slightly smaller: 2.98× 2.55 mm in CD and 9.2 mm in height. Calice slightly elliptical, the GCD:LCD ranging from 1.06–1.21. Sides of corallum almost completely covered by a thin, smooth epitheca, so thin that the underlying costae are clearly outlined, allowing the observation that the C4 originate by trifurcation with the C3 on the lower third of the corallum. The epitheca terminates about 0.3 mm from the calicular edge, distal to which are costae 0.12–0.15 mm wide and separated by deep, thin (0.03–0.04 mm) intercostal grooves characteristic of a turbinoliid. The sides of the costae bear very small (20 µm tall) blunt spines ( Fig. 8K).

Septa hexamerally arranged in 4 incomplete cycles according to the formula: S1>S2–3>S4. Most coralla above a GCD of 2.0 mm contain 44 septa, lacking 2 pairs of S4 on opposites sides of the lateral half-systems. Only one corallum of GCD 2.41 had more septa: 46. A corallum of a GCD 1.8 mm has 36 septa and one of GCD 1.30 has 24. All S4 pairs are inserted into the end half-systems before any occur in the lateral half-systems. S1 moderately exsert (0.65 mm), having vertical sinuous axial edges. S2–3 less exsert, about 80% the width of an S1, also having sinuous axial edges. In some specimens, S3 slightly less wide then S2. S4 least exsert septa, about 65% width of an S1, and have straight axial edges. Fossa shallow, containing a variable number of elements ranging from 2 to 18. In most coralla there are 6 paliform lobes (P2) forming an elliptical crown before the S2, each of which is irregular in shape (not lamellar) and about 0.15 mm in diameter. Most coralla also have 2–6 larger (0.3 mm in diameter), similarly irregularlyshaped rods arranged in a rhomboidal to linear pattern, some, but not all, seemingly adjacent to various S1, resulting in a total of 8–12 fossular elements. These larger rods are interpreted as columellar rods. Finally, in a low percentage of coralla (e.g., the holotype), there is a small rod before some of the S3 that are flanked by pairs of S4, the largest number being eight in the holotype. These are interpreted as paliform lobes and not pali, the latter the result of septal substitution, as their presence is very erratic and often absent even when pairs of S4 are present. The holotype has 6 P2, 8 P3, and 4 columellar elements, for a total of 18 fossular elements ( Figs. 8F,G).

Etymology. curvatus, Latin “curved”, an allusion to the curved corallum of this species.

Distribution. Marion Plateau, Queensland, 342– 367 m.