Trochocyathus (Trochocyathus) cooperi (Gardiner 1905)

Trochocyathus cooperi (Gardiner, 1905), comb. nov

Tropidocyathus cooperi Gardiner, 1905:955, pl. 93: fig. 30.

Trochocyathus.—Vaughan and Wells, 1943:48, fig. 20b.

DESCRIPTION.—Corallum (anthocyathus) a highly compressed (GCD:LCD = 1.4–2.3), straight cylinder, with parallel thecal edges and only slightly divergent thecal faces. Largest Japanese specimen 13.4 × 8.6 mm in calicular diameter and 18.5 mm in height. Base of each thecal edge bears a downward projecting crest up to 4.5 mm in length and flattened in plane of GCD. Between these 2 crests is the basal scar of attachment, which is elliptical to almost circular: 3.9–4.3 × 3.3–3.4 mm in diameter. Only one small specimen is fully intact, still having its anthocyathus attached to the fixed anthocaulus. It measures 7.3 × 3.9 mm in calicular diameter and 8.0 mm in height, with 2 edge crests, but it is assumed that the eventual transverse division would have taken place about 3.3 mm from the basal disc, just under the edge crests, where the cross sectional diameter is about 4 × 3 mm. The holotype also has a partial anthocaulus remaining attached to its base. Costae equal in width (0.5 mm), flat, and granular (about 2 granules across a costa), becoming slightly convex and separated by deeper furrows near calicular edge. Corallum reddish brown, with slightly more intense color and dark costal speckling in a narrow band about 1.5 mm from the calicular edge.

Septa hexamerally arranged in 4 complete cycles: S1–2>S3>S4 (48 septa); however, larger coralla often have pairs of S5 in the end half-systems comprising up to 56–62 septa. S1–2 little exsert (about 0.7 mm), extend about two-thirds distance to columella, and have slightly sinuous inner edges. A slender (about 0.6 mm wide) palus sometimes occurs on the inner edge of each S1–2, forming a deep-seated palar crown directly adjacent to the columella, but often these pali are missing or indistinguishable from columellar elements. S3 only slightly less exsert (0.6 mm), about two-thirds width of S1–2, and have sinuous inner edges. Each S3 bordered by a wide (up to 1.1 mm) palus, together forming a prominent palar ring encircling columella. S4 0.5 mm exsert and about three-quarters width of an S3. When present, pairs of S5 are quite small. Fossa of moderate depth, containing an elongate columella consisting of several papillae, some of which may be indistinguishable in size and position with P1–2.

Trochocyathus cooperi est une espèce de coraux appartenant à la famille des Caryophylliidae. Selon la base de données WoRMS, Trochocyathus cooperi fait partie du sous-genre Trochocyathus (Trochocyathus) Milne Edwards & Haime, 1848.

azooxanthellate

25-100 m