Mangana canui (Silén, 1941) n. comb.

(Figs 12, 13; Table 13)

Callopora canui Silén, 1941: 34, figs 36–40, pl. 3, fig. 8.

Material examined. Holotype by original designation UPSZTY 2459 (poorly preserved, not figured) Okinose, Sagami, Japan; depth 300–600 m. Leg. Prof. S. Bock 1914. Paratypes UPSZTY 191145 (Fig. 12), UPSZTY 191146 (Fig. 13B), same details as the holotype. Paratype UPSZTY 191147 (Fig. 13A) Okinose, Sagami, Japan; depth 100 m. Leg. Prof. T. Gislén, Pacific Expedition 1930–1931.

Description. Colony encrusting, multiserial, unilaminar. Interzooidal communication through multiporous septula visible on the lateral and distal inner wall (Fig. 13B), 35–45 µm long by 20–25 µm wide, with 2–4 pores per septulum, 5–10 µm in diameter.

Autozooids oval, slightly longer than wide (mean L/ W 1.19), distinct, separated by thin grooves (Fig. 12A), quincuncially or irregularly arranged. Gymnocyst negligible laterally, only visible in zooids in formation (Figs 12C, 13B), smooth; opesial cryptocyst sloping inwards, narrow, about the same width proximally and laterally (45–65 µm), tapering distally, coarsely granular with granules arranged in radial rows, 7–10 µm in diameter, the raised beaded outline formed by smaller granules, 2–6 µm in diameter; frontal surface made of areas of granular interior wall (with scattered pores) due to secondary calcification originating from interzooidal chambers assumed to be kenozooids.

Opesia oval, occupying most of the frontal surface (mean OpL/ZL 0.81), constantly with two distolateral spine bases indenting the cryptocyst (Fig. 12B), persisting also in ovicellate zooids (Figs 12E, 13A), basal diameter 14–30 µm.

A large frontal avicularium obliquely placed proximally to proximolaterally on each autozooid (Fig. 12A, B); areas of granular interior wall seen on the surface of some cystids, in some instances, overlapping with the ooecium of the preceding zooid (Figs 12E, F, 13A); rostrum raised at about 45° from the surface of the colony, outer sides smooth, directed distolaterally to either side, its edges serrated, hooked at the tip (Fig. 12D); mandible triangular also with hooked tip (Fig. 13A), 210–270 µm long; crossbar seemingly complete. In some autozooids, two avicularia similar in shape but smaller in size (160–250 µm long by 80–100 µm wide) occupy the proximal frontal area (Fig. 12C). Rarely, even smaller avicularia (c. 75 µm long by 50 µm wide) are present at the intersection among three autozooids (Fig. 12B, C).

Ovicells slightly convex, mostly immersed in proximal part of distal zooid, not closed by the operculum; ectooecium granular, partially calcified, progressively closing, leaving only a narrow straight to arched fissure centrally to proximally (125–205 µm long by 15–50 µm wide) with a raised, sometimes flared rim through which the smooth endooecium is visible (Figs 12E, F, 13A).

Remarks. This species showcases the key traits of the family Foveolariidae, namely a negligible gymnocyst and a bipartite cryptocyst (Winston 2005; Martha et al. 2020). The inner granular portion of the cryptocyst steeply encircles and slopes into the opesia, while the perforated outer portion appears as a thin-layered kenozooidal overgrowth on the sides of avicularia and ovicells with the kenozooids being formed adventitiously in interzooidal furrows. Among all the genera of foveolariids, it is here assigned to Mangana primarily because of two features typical of this genus (Gordon 2014), i.e. the presence of multiporous septula on the distal and lateral walls of autozooids (Fig. 13B), and the presence of large adventitious avicularia proximally on each autozooid (Fig. 13D).

The type species of the genus, M. magnesia Gordon, 2014, differs from M. canui n. comb. in having oligoserial (i.e. bi- to triserial) colonies and in the lack of oral spines. These characters, however, do not appear to hold significant taxonomic importance at generic level, as numerous cheilostome genera include species with varying colony arrangements (uniserial, oligoserial and multiserial) and the presence and absence of spines. Additionally, the latter character often shows intracolonial variability and may be ephemeral in nature.

Mawatari (1952) reported this species from several sites off the Kii peninsula but in his specimens the distolateral spines, constantly present in the type material, were lacking.