Trimuricea flava Samimi-Namin & Ofwegen, 2016, n. sp.

Trimuricea flava n. sp.

(Figs. 4 d, 9–12, 31a–b) Description. The holotype is 20 cm high and 21.5 cm wide, branched in one plane, and many anastomoses are present forming a network; the meshes of the network are mostly elongate (Fig. 4 d). The stem is about 0.5 cm long and thick and the branches are 3–4 mm thick. The calyces are dome shaped, arranged closely together and situated all around the branches. They are low, only a few mm tall and a have diameter of up to 1 mm.

The points have triradiates (Fig. 9 a), along with curved, hockeystick or boot-shaped sclerites, or spindles (Fig. 9 b), 0.13–0.30 mm long. The upper ray of the triradiates and upper part of the spindles is slightly echinulate for up to 0.10 mm (Fig.9 a). The collaret spindles are 0.15–0.40 mm long (Fig. 9 c); the middle part of the convex side is slightly more tuberculate than the concave side and both ends. These polyp sclerites have strong tuberculation. A few tentacle scales are present, up to 0.13 mm long.

The calyces have thornscales, 0.15–0.50 mm long, with an echinulate or tuberculate thorn up to 0.15 mm long (Fig. 10 a). Some of these thornscales have more than one thorn. The thornscales have complexly branched roots.

The coenenchyme has spindles, 0.30–0.7 mm long, with simple, and complex, densely placed tubercles (Fig. 10 b). Several of these spindles have side branches or a few thorns.

Colour. In live colonies the extended polyps are yellow (Fig. 31 a, paratype) but the colonies appear as more orange when the polyps are retracted (Fig. 31 b, paratype); preserved colonies are brown. All sclerites are faintly yellow.

Etymology. The specific epithet is derived from the Latin flavus (gold-coloured, yellow). It refers to the colour of the polyps and the colonial sclerites.

Remarks. One of the paratypes RMNH Coel. 39862 has a side fan perpendicular to the main fan. It also has slightly longer coenenchymal spindles than the holotype (Fig. 12 b). It also contains thornscales with slightly more complex thorns (Fig. 12 a). The polyp sclerites are also more complexly warted (Fig. 11 b).

The live colony of one of the paratypes, RMNH Coel. 41668, was slightly different from the other specimens. It was dark orange to magenta in some parts of the colony (Fig. 31 b).

Trimuricea flava n. sp. resembles T. spinosa n. sp., as both species have thornscales possessing more than one thorn, and similar looking coenenchymal spindles. Trimuricea spinosa differs in having colourless sclerites, triradiates with a strongly echinulate ray, and less tuberculate collaret spindles. Due to its longer and more complex coenenchymal spindles, the other paratype of Trimuricea flava has considerable resemblance to T. merguiensis and T. tuberculosa n. sp. However, both of these species differ from Trimuricea flava in having colourless sclerites. Trimuricea merguiensis further differs in having coenenchymal spindles with a blunt end, and T. tuberculosa in having coenenchymal sclerites that include small, irregularly forms and triradiates and crosses.

This is the only species of the genus having coloured sclerites.