Reteporella watersi Denisenko et al. 2016

Reteporella watersi (Nordgaard, 1907)

(Fig. 5; Table 3)

Retepora beaniana var. watersi Nordgaard, 1907: p. 16; Kluge 1962, p. 529, 530, fig. 370.

Reteporella watersi: Hayward 1994: p. 195, fig. 8A, B; Hayward & Ryland 1996: p. 111, fig. 3B; Hayward & Ryland 1999: p. 376, 377, fig. 178A–C.

Material examined. ZIN 4 /50741, one colony; Stn 2016_PA_4_40 (61.9967333475749° N; ‒ 41.0106666664283° W; 234 m; T 3.9 °C); MT Paamiut, collected by Alfredo III trawl; fish-shrimp trawl assessment survey. July 2016. ZIN 5 /50745, one colony fragment; Stn 2016_PA_1_22 (64.5355499903361° N; ‒ 55.1436500072479° W; 563 m; T 4.12 °C); MT Paamiut, collected by BEAMTRAWL; fish-shrimp trawl assessment survey. July 2016.

Description. The colony is reticulate, funnel-shaped, thickly calcified, robust and matte, up to 50 x 40 mm in size. The branches consist of 3–5 alternate series of zooids, increasing twice in width at points of fusion. Fenestrulae are relatively small, approximately 0.7‒0.9 mm long by 0.2–0.6 mm wide (Fig. 5A; Table 3). The basal surface is covered by kenozooids delimited by prominent vibices (Fig. 5B); the frontal and abfrontal surfaces are deeply pitted with a honeycomb structure.

Autozooids (L = 0.35–0.75 mm; W = 0.25–0.42 mm) are located in the inner part of the funnel and delimited by sutures. Several large areolar pores are located near the zooidal margins.

The orifice is wider than long, with a straight proximal margin; the upper distal rim is smooth and with short blunt denticles below (Fig. 5C). The orifice is partly hidden by a peristome, which has two unequal lobes that close to form a circular pseudosinus. The larger lobe bears an oval avicularium directed proximolaterally.

The suboral avicularium is more or less parallel to the zooidal surface with a tall rim, and a few teeth on the distal rostrum; it has a complete crossbar without columella; the palate is a narrow shelf (Fig. 5C, D, F). Oral spines were not observed. The frontal avicularia are slightly smaller than the suboral ones, oval or roundish with complete crossbar and no columella.

The ovicell is immersed, longer than wide, with a pronounced quadrate labellum and an elongate median fissure, mostly covered by pitted extrazooidal calcification during ontogeny (Fig. 5E).

Remarks. The suite of characters observed in R. watersi, recently obtained from around Greenland, fits well with previous descriptions of specimens from the Faroe area (cf. Hayward 1994; Hayward & Ryland 1996, 1999). Nevertheless, some discrepancies in skeleton morphology were observed, such as the absence of oral spines in our specimens, which were also lacking in the description by Kluge (1962), as well as in the original description of the species by Nordgaard (1907). The measurements of the specimens analyzed here are also different from those presented in the literature, where zooids and orifices are narrower.

Distribution. Sublittoral, deeper than 200 m in the waters south and northwest of Greenland. Around Faroe Islands at 68 stations, and in Iceland waters at 80 stations, at depths between 210 and 1112 m.