Scrupocaberea contraria, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Scrupocaberea contraria sp. nov.

Di Martino, Rosso and Taylor

Figure 14 View FIGURE 14

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Type material. Holotype PMC. B49. 29.7.2024 a, sample 19032 ( Figure 14C–E View FIGURE 14 ); paratype PMC. B49. 29.7.2024 b1, sample 19065 ( Figure 14A–B, F–G View FIGURE 14 ); paratype PMC. B49. 29.7.2024 b2, sample 19023 (not figured); Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Etymology. Latin, meaning opposite, referring to the change in direction (from proximolateral to distolateral) of the frontal avicularia when the proximal zooid is ovicellate.

Diagnosis. Scrupocaberea with rounded rectangular or club-shaped autozooids; smooth extensive proximal gymnocyst, short smooth cryptocyst bordering the proximolateral margins of opesia; bean-shaped opesia with two faint distolateral spines, one on each side, typically hidden in ovicellate zooids; lung-shaped scutum nearly completely covering the proximal portion of opesia, with robust attachment base; frontal avicularium small, drop-shaped, placed at zooidal mid-length on the inner side, adjacent to the proximolateral margin of the opesia, directed proximolaterally when distal to a non-ovicellate zooid, shifting to distolateral when distal to an ovicellate zooid; frontal giant avicularium rare, placed atop a raised cystid; lateral avicularium also small and drop-shaped; ovicells with large semicircular ectooecial fenestra with concave proximal margin; dorsal side with tulip-shaped vibracula with oblique, slightly curved setal groove.

Description. Colony erect with narrow biserial branches (245–295 µm wide) transitioning to triserial at bifurcations (460–480 µm wide); branches rectilinear to slightly curved, flat, subelliptical in cross-section; articulating nodes not observed. Autozooids distinct, separated by shallow grooves, rounded rectangular to club-shaped, elongate (mean ZL/ZW 2.61), arranged alternately in two longitudinal series. Proximal gymnocyst smooth, extensive; cryptocyst smooth, slightly depressed, relatively wide proximally, tapering laterally, absent distally. Opesia bean-shaped, occupying slightly less than half of the frontal surface (mean OpL/ZL 0.42) with two faint distolateral spines, one on each corner, 8–16 µm in diameter at the base, typically concealed in ovicellate zooids. Scutum originating laterally from the inner side, attached at about half the opesia length, covering nearly the entire proximal portion and leaving a semicircular to rounded rectangular orifice distally, lung-shaped, with a robust attachment structure measuring 52–95 µm in width. Adventitious avicularia small, drop-shaped, occurring in two types: a single (sometimes absent) frontal avicularium, at the distal termination of the gymnocyst leaning on the lateral zooidal corner, on the inner side of the branch, and adjacent to the opesia, possibly modifying the outline of the cryptocystal rim, positioned on a lozenge-shaped slightly raised cystid, with an acutely triangular rostrum directed proximolaterally, changing orientation to distolateral when distal to an ovicellate zooid; giant frontal avicularium rarely present, located atop a smooth, raised cystid constricted at the base (44 µm wide) and enlarged distally (116 µm wide); constant lateral avicularium positioned on a small conical cystid, with an acutely triangular rostrum directed laterally and sloping downward; all avicularia with small condyles. Ovicells globular, occupying the entire proximal gymnocyst of the distal zooid, modifying its cryptocystal rim; ooecium smooth with a partially calcified ectooecium, featuring a central large semicircular fenestra with a concave proximal margin, 68–100 µm long by 84–120 µm wide, exposing the endooecium. Dorsal side occupied by tulip-shaped vibracula with a long, obliquely placed, slightly curved, deep setal groove, and a shallow undulose median furrow corresponding to zooidal boundaries; each vibraculum with a medium-sized, circular to transversely elliptical radicular pore measuring 18–22 µm in maximum diameter, located proximally on the outer side.

Measurements (µm). ZL 413±13, 395–438 (1, 10); ZW 158±22, 124–195 (1, 10); GymL 165±12, 153– 195 (1, 12); CryL 50±9, 41–72 (2, 17); OpL 175±12, 153–198 (2, 17); OpW 80±9, 65–97 (2, 17); AvL (frontal standard) 48±7, 36–57 (2, 16); AvW (frontal standard) 31±5, 24–39 (2, 16); AvL (frontal enlarged) 216 (1, 1); AvW (frontal enlarged) 116 (1, 1); AvL (lateral) 34±2, 31–36 (2, 5); AvW (lateral) 20±4, 14–24 (2, 5); ScuL 126±16, 106– 156 (2, 14); ScuW 65±10, 48–80 (2, 16); OvL 177±7, 166–185 (1, 8); OvW 166±13, 139–186 (1, 8); VibrL 243±26, 198–284 (2, 10); VibrW 127±18, 92–142 (2, 10).

Remarks. Two Scrupocaberea species were found in Daidokutsu cave: S. contraria sp. nov. and S. maderensis (Busk, 1860) (see description below and Figure 15 View FIGURE 15 ). These species mainly differ in the texture of the cryptocyst, which is smooth in S. contraria sp. nov. and granular in S. maderensis , the shape of the ectooecial fenestra, which is large, semicircular and crescent-shaped in S. contraria sp. nov. but small and circular to elliptical in S. maderensis , the number and position of the opesial spines, with two faint distolateral spines, one on each corner, in S. contraria sp. nov., and two spines on the inner and three on the outer distolateral corners in S. maderensis . Additionally, the dorsal side differs in the shape, size and location of the vibracula with respect to the zooid to which they are associated. The general appearance of the branch is also very different, being serrated in S. maderensis and more linear in S. contraria sp. nov.

The ectooecial fenestra of S. contraria sp. nov. resembles that of Canda lunata sp. nov., and both species exhibit a change in avicularia orientation when distal to an ovicellate zooid.

Compared to other known Scrupocaberea species, S. contraria sp. nov. has distinct features: S. dongolensis ( Waters, 1909) from Sri Lanka shares a similar scutum and zooidal shape, and frontal avicularia in similar position, but has a greater number of more robust outer distolateral spines, larger lateral avicularia, and a significantly reduced ectooecial fenestra ( Vieira et al., 2014). Similarly, S. ornithorhynchus ( Thomson, 1858) from Australia also has a very reduced fenestra, large lateral avicularia, and a denticulated margin of the opesia in ovicellate zooids ( Vieira et al., 2014). Scrupocaberea gilbertensis (Maplestone, 1909) from the southwest Pacific differs by having a granular cryptocyst ( Vieira et al., 2014).