Puellina paracaesia Yang & Seo & Min & Grischenko & Gordon 2018, n. sp.

Puellina paracaesia n. sp.

(Figs 30–33)

Material examined. Holotype: NIBRIV0000805953, N of Soan Island, South Sea, 34.2305° N, 126.6486° E, 29 July 2016, 37 m depth. Paratype: NIBRIV0000812251, 37.9378° N, 124.6233° E, 27 November 2007, 0.3 m depth. Other material: Baengnyeong Island: Dumujin, 2 colonies; Yeonhwa-ri, 1 colony. South Sea: Wan Island, 1 colony; Cheongsan Island, 3 colonies. Also a colony from western Kamchatka slope, Sea of Okhotsk, 58.017° N, 155.717° E, 290 m depth.

Description. Colony encrusting, unilaminar, multiserial, up to 15.5 mm across, whitish-transparent. Autozooids roughly suboval with truncate or angled proximal margins, widest mid-length or in proximal third. Frontal shield comprising 9–11 (mostly 10) costae (including suboral pair), midline fusions irregular, subnodular, with no clear boundaries, often with irregular central peak; 2–3 lacunae between adjacent costae, proximal ones rounded with emergent papillae; the others reniform owing to tiny ligula. Gymnocyst well developed proximally and proximolaterally, not laterally. Orifices dimorphic, that of the female seen to be longer and wider in zooids in which ooecium not yet developed. Autozooidal orifice transversely D-shaped, wider than long, proximal margin straight, not clearly formed by first pair of costae, which appear to overlie it; these costae narrow, defining very small median suboral ligulate pore (lacuna) in most zooids; bordered by 3–5 articulated oral spines. Interzooidal avicularia not seen. Ooecium subprominent, glabrous, with median crest or elevation; 2 oral spines present. Up to three small basal pore chambers on each distolateral side of zooids at colony margin. Ancestrula tatiform with 11 evenly distributed spines, the mid-proximal one longest, curving over proximal half of opesia. Periancestrular zooids with 5 oral spines.

Measurements. ZL, 191–281 (239) µm; ZW, 151–244 (177) µm; OrL, 19–24 (22) µm; OrW, 40–52 (46) µm; OoL 87–122 (102) µm; OoW 112–138 (128) µm.

Remarks. Our material resembles P. caesia Dick, Grischenko & Mawatari, 2005 from Alaska in the number of oral spines (3–5), a relatively low number among Puellina species. On the other hand, the reniform intercostal lacunae in P. paracaesia n. sp., each with a tiny ligula, are very distinctive. Additionally, there are two concentric rings of intercostal pores inside the ring of larger papilla pores (typically only one such concentric ring of intercostal pores in P. caesia) and zooid size in the Korean material is 3/5 (zooid length) and 2/3 (zooid width) that of P. caesia at Ketchikan. While colony color is not necessarily a reliable character, the Ketchikan specimens were conspicuously gray—hence the name caesia —whereas P. paracaesia n. sp. is whitish transparent and the orifice is more compressed proximodistally. The number of costae overlaps but can be higher (up to 14) in Alaskan material. It is likely that these two taxa represent trans-Pacific sister species.

Distribution. Korea, western Kamchatka, 0–290 m depth. Puellina paracaesia n. sp. has also been found in the eastern part of the Sea of Okhotsk (A.V. Grischenko, pers. obs.).