Glabrilaria ossuosa, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Glabrilaria ossuosa sp. nov.

Di Martino, Rosso and Taylor

Figure 20 View FIGURE 20

zoobank.org/ F5D22272-058D-48AE-B629-E69B4164CB60

Type material. Holotype PMC. B51. 29.7.2024 a, sample 19071 ( Figure 20A–D View FIGURE 20 ); paratype PMC. B51. 29.7.2024 b, sample 19053 ( Figure 20E–F View FIGURE 20 ); Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Etymology. Latin, meaning bony, referring to the narrow, sharp, angular appearance of the costae.

Diagnosis. Glabrilaria with 14–17 narrow, angular, ridged costae, 3–8 intercostal lacunae, single, minute, flat pelmatidium at the outer end of each costa, large rounded-to-kidney-shaped oral lacuna without a mucro; seven oral spine bases in autozooids, four retained in ovicellate zooids; single or paired adventitious, semi-erect latero-oral avicularia with a needle-like rostrum, directed distolaterally medially, either transversely positioned on the costate frontal shield of the distal zooid or covering one side of the ovicell; ooecium globular, smooth, with central suture beginning proximally and closing around mid-length.

Description. Colony encrusting, multiserial, unilaminar. Autozooids distinct, separated by shallow grooves, oval to rhomboidal, occasionally polygonal, longer than wide (mean ZL/ZW 1.33). Frontal shield flat to slightly convex, consisting of 14–17 (mean 15) costae including suboral pair; costae narrow, angular, ridged, with a maximum basal width of 17–29 µm, tapering and converging towards the centre, along an undulate midline; each costa with a minute, flat, circular pelmatidium, measuring 2–4 µm in diameter, at its outer end. Costae connected by intercostal bridges creating 3–8 elliptical intercostal lacunae, 11–17 µm in length. Suboral pair of costae greatly reduced, forming a large, rounded to kidney-shaped suboral lacuna, measuring 8–16 × 12–27 µm; in some instances the suboral costae not fusing, creating a trifoliate lacuna, while in other cases bifurcating and meeting at two separate points, resulting in two lacunae of different sizes, with the distalmost larger than the proximalmost; suboral costae flat, not forming a suboral mucro. Gymnocyst exposed along zooidal margins, typically wider proximally, 28–81 µm in length. Orifice transversely D-shaped with straight proximal margin; seven, regularly spaced oral spine bases, 10–14 µm in diameter, with the proximalmost pair placed slightly above the proximal oral margin. Avicularia teardrop-shaped, mostly paired, occasionally single, semi-erect, emerging from basal pore chambers lateral to the orifice, positioned at the same level as the suboral or rarely the second distalmost pair of costae; rostrum slender and needle-like, oriented distolaterally and medially, either resting on the costate frontal shield of the distal zooid or occupying one side of the ovicell; small mandibular pivots present. Ovicell hyperstomial, globular, either kenozooidal with the kenozooid not visible in frontal view, or formed by the distal autozooid; ooecium smooth, with median suture beginning proximally and closing at about halfway along its length. Kenozooids present, typically polygonal, often rounded triangular, with reduced costate shield of 10 radial costae and 3–5 intercostal lacunae. Pore-chamber windows visible along lateral walls of zooids at colony periphery, rounded to elliptical, 6– 75 µm long by 5–50 µm wide.

Measurements (µm). ZL 321±34, 265–396 (3, 20); ZW 241±37, 192–310 (3, 20); GymL 51±13, 28–81 (3, 20); OL 51±3, 48–57 (3, 18); OW 66±4, 61–72 (3, 18); AvL 100±28, 59–162 (3, 20); AvW 35±3, 31–41 (3, 20); OvL 103±16, 76–128 (2, 16); OvW 148±13, 113–163 (2, 16); KzL 181±52, 145–218 (1, 2); KzW 167±86, 107–228 (1, 2).

Remarks. Glabrilaria ossuosa sp. nov. shares several characteristics with the two other cribrilinid species identified in the Okinawa core samples. It resembles G. biavicularia in the appearance of its costate frontal shield, which consists of narrow, angular costae, and in the presence of adventitious latero-oral avicularia. However, G. ossuosa sp. nov. differs from G. biavicularia in the number of oral spines, consistently seven in the former species, consistently five in the latter species, in the shape of the pelmatidium, flat in G. ossuosa sp. nov. and tubercular in G. biavicularia , and in the shape of the orifice, which is more elongate in G. biavicularia (mean OL/OW 0.92 in G. biavicularia vs 0.78 in G. ossuosa sp. nov.). In addition to these differences, the suboral area of G. biavicularia is also very distinctive.

Glabrilaria ossuosa sp. nov. also shares the consistent number of oral spines with Cribrilaria harmeri , both having seven. They differ in the ooecium type, that if kenozooidal in C. harmeri generally has a visible kenozooid, which is not apparent in G. ossuosa sp. nov. In addition, G. ossuosa sp. nov. lacks interzooidal avicularia and the adventitious avicularia are differently directed.

The new species differs from all other Glabrilaria with seven spine bases. Glabrilaria africana (Hayward and Cook, 1983) , from South Africa, has a tubercular pelmatidium, an oooecium with an umbo, and a suboral area containing up to five large pores along with several smaller ones. Glabrilaria antoniettae Ramalho and Moraes, 2021 , found in the West Atlantic off the coast of Brazil, has a distinct suboral mucro and avicularia with pronounced serrations of rostra. Glabrilaria corbula Bishop and Househam, 1987 , described from the English Channel, is distinguished by its ooecium, which has radial ridges and lacks a median suture, and avicularium with a curved rostral tip forming a beak-like projection. Glabrilaria hirsuta Rosso in Rosso et al., 2018b, also from the West Atlantic, has a spiny costate frontal shield. Glabrilaria septemspinosa (d’Hondt, 1986) comb. nov. from New Caledonia, has fewer costae compared to G. ossuosa sp. nov., as well as differently directed avicularia.