Sphenotrochus cuneolus, Cairns, 2004

Cairns, S. D., 2004, The Azooxanthellate Scleractinia (Coelenterata: Anthozoa) of Australia, Records of the Australian Museum 56, pp. 259-329 : 299-300

Sphenotrochus cuneolus n.sp.

Figs. 9A–F

Sphenotrochus hancocki .– Cairns, 1989a: 38–39 (in part: Albatross -5145).

Records/Types. Holotype: Franklin 03/99/D11, AM G16746 . Paratypes: Franklin 03/99/D8, 1, USNM 1008848 ; Franklin 03/99/D10, 6 (including SEM 999 ), USNM 1008849 ; Franklin 03/99/D11, 6: 5, USNM 1008850 and 1, ZMUZ; Alb - 5145, 1, USNM 81896 . Type Locality: 20°14.49'S 151°47.53'E ( Marion Plateau , Queensland), 342 m.

Description. Corallum cuneiform, with planar thecal faces and rounded thecal edges and base, the edges being roughly parallel. Largest specimen (holotype) only 1.43× 1.02 mm in CD and 2.78 mm in height, but judging from the high frequency of juvenile forms of other turbinoliids taken at this site, this may also represent a sub-adult size. Calice elliptical, the GCD:LCD about 1.4. Costal arrangement distinctive and consistent ( Figs. 9B,C). The 12 C1–2 are continuous, all reaching the base of the corallum. The medial C2, which bisect the lateral faces, and the principal C1, which are on the corallum edges, are straight, whereas the 4 C1 and C2 on each face between the medial C2 and principal C1 curve slightly inward near the base of the corallum and then abruptly outward, producing a moderate sinuosity. C3 also continuous but do not extend entire distance to the base, their length progressively increasing away from the medial C2: those C3 adjacent to the medial C2 extend about 60% of the distance to the base, the next pair of C3 toward the principal C1 being slightly longer (about 65% of the distance to the base), and those C3 directly adjacent to the principal C1 extend about 75% to the base. Costae uniform in width and ridge-like, 0.06–0.07 mm in width, and separated by broad intercostal spaces about 0.09 mm in width. A series of small pores, each 10–11 µm in diameter, occurs along both edges of each intercostal region ( Fig. 9D), each pore separated by 35–40 µm from one other and alternating in position from those on the opposite side of the intercostal space. Corallum white.

Septa hexamerally arranged in 3 complete cycles, resulting in 24 septa (S1–2>S3). All specimens reported dead when collected and thus not optimally preserved, but S1–2 equal in exsertness and width, having quite sinuous axial edges, the lower edges of which fuse to the columella in the case of the 6 S 1–2 in the lateral corallum position. S3 considerably smaller and have straight axial edges. Fossa shallow, containing a robust, lamellar columella, the upper edge rising above the calicular edge.

Remarks. Among the nine Recent species in the nominate subgenus of Sphenotrochus , defined as those species bearing costae that are continuous (not fragmented into numerous short carinae, see Cairns, 1997), S. cuneolus is most similar to S. hancocki Durham & Barnard, 1952 , a species known from throughout the tropical Pacific at 18–274 m ( Cairns, 1989a). These two species are similar in size and septal and columellar morphology, but S. cuneolus differs in its costal arrangement and in having sinuous axial edges of its S1–2. SSphenotrochus hancocki not only has a different arrangement of costae but also a fragmentation of its costae near the base.

Etymology. cuneolus, Latin for “small wedge”, an allusion to the small size of this cuneiform coral.

Distribution. Marion Plateau, Queensland; SuluArchipelago, Philippines; 42– 342 m.