Encrusting Star Coral

Coenocyathus bowersi Vaughan, 1906

Coenocyathus bowersi Vaughan, 1906a:847, pl. 77: figs. 1–3.—Durham, 1947:34.—Durham and Barnard, 1952:83–84, pl. 10: fig. 45a-d.—Wells, 1956:F422, fig. 323, 8.—Squires, 1959:422.—Parker, 1964:150.—Zibrowius, 1980:73.—Austin, 1985:81.—Bythell, 1986:14–15, pl. 3: fig. A; pl. 5: figs. A–F, color cover illustration.—Cairns et al., 1991:47.

DESCRIPTION.—Corallum colonial, the most common habit being a thick mounded coenosteal encrustation from which cylindrical corallites arise by extratentacular budding, each corallite 5–8 mm in height. However, some colonies have widely spaced and taller (up to 20 mm) corallites (Plate 8b) and others have closely spaced (cerioid) and very short corallites (Plate 8a). One corallum (Plate 8c) even adopted a branching mode, some of its corallites budding from the theca of parent corallites. Holotypic colony only 4 cm in width; however, Durham (1947) reported a colony 1 foot (30.5 cm) in diameter, and a specimen at the CAS (77797) measures 37 cm across. Colonies usually encrust bivalves or rocks. Calices usually circular, but may be elliptical or somewhat irregular in shape. Calice size quite variable, some colonies (e.g., the holotype) having corallites 3.5–7.5 mm in calicular diameter, others averaging up to 13–14 mm in diameter. In addition to the typical method of extratentacular budding, examples of intratentacular budding are found in most coralla, in which a corallite is in the process of or has split into two or as many as 10 smaller corallites (Plate 8d,e), a process termed multiple fission by Durham and Barnard (1952). Costae broad and flat to slightly convex, equal in width, and separated by very narrow, slender striae. Costae sometimes extend over coenosteal base. Corallum white.

Septal symmetry extremely irregular. Each calice has 6–14 primary septa, which are larger than all others and extend to the columella or center of calice, dividing the corallite into 6–14 sectors. Each sector encloses 3, 5, or 7 septa. The 3-septa-sectors consist of 1 secondary and 2 smaller tertiary septa plus 1 P2. The 5-septa-sector consists of 1 secondary, 2 tertiary, and a pair of small quaternary septa, plus 1 P2. The 7-septa-sector consists of 1 secondary, 2 tertiary, and two pairs of quaternary septa, accompanied by 2 P3. Some calices have a typical hexameral symmetry of 12 primary, 12 secondary, and 24 tertiary septa with 12 P2 (48 septa, Plate 8f), but most calices have a mixture of developmental stages, producing a very irregular septal insertion pattern, but no corallite examined had over 56 septa. All septa little exsert and have slightly sinuous inner edges. Pali (P2 or P3) relatively slender and extremely sinuous. In some calices they form a well-defined crown (Plate 8f) as in Caryophyllia, but in others pali are poorly formed or even missing in various sectors.

Fossa of moderate depth, containing a small fascicular columella composed of 1–4 twisted laths. Occasionally the columella is absent, the inner edges of the primary septa being slightly expanded and almost meeting in center of calice.

azooxanthellate

9-302 m