Conocyathus formosus, Cairns, 2004

Cairns, S. D., 2004, The Azooxanthellate Scleractinia (Coelenterata: Anthozoa) of Australia, Records of the Australian Museum 56, pp. 259-329 : 290

Conocyathus formosus n.sp.

Figs. 5F–H, 6A–C

Records/Types. Holotype: Franklin 03/99/D11, 20°14.49'S 151°47.53'E ( Marion Plateau , Queensland), 342 m, (type locality), AM G16743 . Paratypes: Franklin 03/99/D8 (Marion Plateau), 1, USNM 1008829 ; Franklin 03/99/D10, 12, USNM 1008830 ; Franklin 03/99/D11, 48: 43 (including SEM stub 1005), USNM 1008831 , 2 , ZMUZ, 3, WAM Z20515 ; Franklin, 03/99/12, 3, USNM 1008832 ; Franklin 03/99/D13, 1, USNM 1008833 ; 12°28.3'S 130°50.95'E (Darwin Harbour) , depth unknown, 3, NTM 8138 .

Description. Corallum conical and fairly slender (H:D = 1.62–1.88), with a circular calice and blunt base. Holotype (and largest specimen) 2.76 mm in CD and 4.55 mm in height. C1–2 extend from base to calice; C3 originate independently about 1.3 mm above the base, the C4 about 1.7 mm above the base. Proximal to the origin of each C3 is a short costal ridge about 0.35–0.45 mm in length that is initially aligned with the C3 but distally is curved outward toward its adjacent S1, terminating in the intercostal groove that will be aligned with the future C4, altogether resulting in a zone of 12 such short costal ridges at a height of 1.0– 1.4 mm above the base ( Fig. 6C). In upper corallum C1–3 equal in width (about 65 µm), whereas C4 are about half this width, but all costae equal in height and exsertness. But in the basal part of the corallum, below the origin of the C4, the C1– 3 usually bear thin, continuous lateral ridges that project into the intercostal groove nearly obscuring it and essentially doubling the width of these costae. Intercostal grooves about 75 µm in width near calicular edge and bridged by regularly spaced bars, each bar 60–70 µm in width, delimiting rather deep, elliptical pits that are up to 100×70 µm in diameter, the greater diameter aligned with the groove. Approximately 20 pits occur in each intercostal groove adjacent to a C1.

Septa hexamerally arranged in 3 complete cycles (24 septa) having the septal formula: S1>S2>S3. S1 highly exsert (up to 0.3 mm), with extremely sinuous axial edges ( Fig. 5F) that reach almost to the cental palar structure; S1 about 60 µm thick at calicular edge. S2 equally exsert, about 90% width of an S1, also having quite sinuous axial edges. S3 less exsert (0.15 mm), about 75% the width of an S1, and have sinuous axial edges that fuse with the axial edges of their adjacent S2 deep in the fossa, not easily visible in an intact specimen. Although C4 are well developed, there is no trace of S4. In fact, the region that would correspond to an S4 is slightly grooved internally ( Fig. 5F). All septa bear tall (up to 50 µm), rounded granules on their faces arranged in rows in the crests of the septal undulations. Centre of fossa occupied by 6 robust, lamellar P2, each about 0.25 mm in width, the axial edges of the 6 P2 fused together and altogether forming a single robust axial structure that rises to the level of the calicular edge.

Remarks. As seen in Table 5, C. formosus is distinguished from the two other Recent species in the genus by having flanged costae; tall, but slender C4; sinuous septal axial edges; and pali that rise to the edge of the calice. Not noted in the table is the peculiarity that most specimens bear 12 short, disjunct C3 near the base of the corallum.