Chaperia robusta, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Chaperia robusta sp. nov.

Di Martino, Rosso and Taylor

Figure 7 View FIGURE 7

zoobank.org/ CA4BE9D3-DDBD-4684-A936-3F098A300D92

Type material. Holotype PMC. B45. 29.7.2024 a, sample 19081 ( Figure 7A–D View FIGURE 7 ); paratype PMC. B45. 29.7.2024 b, sample 19059 ( Figure 7E–F View FIGURE 7 ); Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Etymology. Latin, meaning robust, referring to the stout appearance of the autozooids.

Diagnosis. Chaperia with stout autozooids and thick, prominently exposed lateral walls; cryptocyst coarsely granular, extensive, forming both frontal and lateral walls; gymnocyst reduced to a smooth calcification encasing spines and creating vertical ridges separating groups of spines; opesia eye-shaped, occupying less than half of the frontal surface, with robust occlusor laminae; 9–13 distolateral oral spines; tubercular closure plates developing in ancestrula and periancestrular zooids.

Description. Colony encrusting, multiserial, unilaminar. Autozooids distinct, separated by deep grooves, irregularly arranged, rhomboidal, squat, as long as wide (mean ZL/ZW 1.01), with thick, prominently exposed, lateral walls (180–300 µm thick) and small, circular pore-chamber windows at their base. Frontal surface mostly occupied by a well-developed cryptocyst, coarsely granular proximally and finer towards the proximal margin of the opesia, flat to slightly convex; lateral walls made of tubercular cryptocyst; gymnocyst reduced to a smooth calcification encasing the oral spines and forming vertical ridges between spine clusters. Opesia eye-shaped, occupying less than half of zooidal surface (mean OpL/ZL 0.44), with well-developed occlusor laminae positioned around one-sixth of the width of the proximal margin of the opesia on each side; spine bases arranged in an arc along distolateral margin of opesia, with proximalmost pair aligned with or slightly below the proximal margin of opesia; 9–10 spines in the first budded zooids, 9–13 in subsequent ones, each spine bases with two concentric rings and external diameter 40–56 µm. Ancestrula resembling later autozooids but more slender and smaller, 522 µm long by 394 µm wide, opesia 187 µm long by 210 µm wide, with nine spines, budding two zooids, one distally and the other distolaterally; first budded autozooids slightly smaller than subsequent ones, 420–430 µm long by 515–560 µm wide, with opesiae 216–233 µm long by 265–290 µm wide. Closure plates with tubercular texture closing the opesia of both ancestrula and the first two generations of autozooids, leaving uncovered areas lateral to the occlusor laminae. Ovicells and avicularia not observed.

Measurements (µm). ZL 571±91, 439–701 (2, 13); ZW 567±65, 471–688 (2, 13); OpL 254±22, 225– 287 (2, 13); OpW 302±17, 268–321 (2, 13).

Remarks. The stout appearance of the autozooids with thick and granular, exposed lateral walls, the large number of oral spines, and the unique features of the cryptocyst and gymnocyst distinguish this species from all known Chaperia species. Among Chaperia species recorded from Japan, C. acanthina (Lamouroux, 1824) , a species that is widespread and otherwise restricted to the southern hemisphere with the doubtful exception of Japan (Harmer, 1926; Silén, 1941), differs in having fewer spines (e.g., 7–10 in Harmer, 1926; 8–10 in Hirose, 2010; 4–5 in Boonzaaier-Davids et al., 2023), and in the oval shape of the opesia, which also occupies a larger proportion of the frontal surface of the zooids. The unnamed new species of Chaperia from Sagami Bay ( Japan) in Hirose (2010) not only has fewer spines (6–7) but also differs in the general appearance of the zooids having an extensive, oval opesia. Among species with numerous spines, the Indo-Pacific C. judex (Kirkpatrick, 1888) differs in having 15–20 spines (Gordon, 1984; Hayward, 1988), while C. multispinosa Gordon, 1984 , from the Kermadec Ridge and SE Australia, differs in having the spines arranged in two semicircular rows (Gordon, 1984).