Stephanollona pachycondylata, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Stephanollona pachycondylata sp. nov. Di Martino, Rosso and Taylor

Figure 61 View FIGURE 61

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Type material. Holotype PMC. B72. 29.7.2024 a, sample 19185 ( Figure 61A–E View FIGURE 61 ); paratype PMC. B72. 29.7.2024 b, sample 19140 ( Figure 61F–G View FIGURE 61 ); Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Etymology. Greek ‘pachys’, meaning thick, and Latin ‘condylus’, meaning articulation, referring to the robust orifice condyles of this species.

Diagnosis. Stephanollona with 6–7 oral spine bases (four in ovicellate zooids); keyhole-shaped orifice with distinctly elongate anter, distally denticulate, narrow and shallow sinus, and conspicuous condyles; paired or single dimorphic latero-oral avicularia, small and oval, directed laterally or slightly distolaterally outwards, and large and elliptical, directed distally or distolaterally outwards, all with ligulate crossbar; ooecium globular, opening with lateral indentations and short labellum.

Description. Colony encrusting, multiserial, uni- to multilaminar. Autozooids becoming indistinct due to secondary calcification and frontal budding, appearing polygonal, nearly square-shaped, almost as long as wide (mean ZL/ZW 1.11). Frontal nodular, imperforate except for elliptical marginal areolae along lateral and proximal zooidal margins, 20–40 µm in maximum dimension. Orifice terminal, immersed, keyhole-shaped, with short, smooth proximal peristome; anter elongate, denticulated, denticles measuring 6–7 µm in length, placed no further proximally than the proximalmost pair of oral spines; sinus U-shaped, accounting for one-third of the total orifice width; condyles smooth, rounded, conspicuous, outlining the proximal sloping margin of the orifice with distal prominences; 6– 7 distolateral oral spine bases with the proximalmost pair situated above the level of condyles, 21– 33 µm in diameter, four remaining in ovicellate zooids; peristome beginning from the proximalmost pair of spines, usually smaller than more distal pairs. Avicularia adventitious, latero-oral, single or rarely paired, dimorphic; avicularia type 1: large, elliptical, almost parallel sided with rounded rostrum, directed distally or slightly distolaterally outwards, placed at the level of the proximal margin of the peristome, with triangular opesia; avicularia type 2: small, oval, directed laterally or slightly distolaterally outwards, placed more distally than type 1, at the level of the second proximalmost pair of spines, with semicircular opesia; all avicularia with complete, ligulate crossbar and somewhat beaded opesia. Ovicell hyperstomial, globular; ooecium smooth, striated by concentric lines; opening with short labellum and lateral indentations.

Measurements (µm). ZL 510±47, 438–587 (2, 14); ZW 460±37, 397–530 (2, 14); OL (including sinus) 150±8, 140–163 (2, 9); OW 103±4, 97–111 (2, 9); AvL (type 1) 290±32, 253–332 (2, 6); AvW (type 1) 93±13, 77–112 (2, 6); AvL (type 2) 87±7, 77–97 (2, 12); AvW (type 2) 68±9, 56–85 (2, 12); OvL 197±12, 189–206 (1, 2); OvW 244±19, 231–258 (1, 2).

Remarks. This new species differs from the two species of Stephanollona previously identified from the North Pacific: S. eopacifica Soule, Soule and Chaney, 1991 from the northeastern Pacific is distinguished by a wider orificial sinus and avicularia with a toothed rostral tip directed more proximally; and S. boreopacifica Yang, Seo, and Gordon, 2018 , found in South Korea, is characterized by 5– 6 spines, avicularia with a toothed rostral tip, and small, oval avicularia also associated with the ooecium. Among species with 6–7 spines, S. ignota (Hayward and Cook, 1983) from eastern South Africa, differs in having avicularia directed distomedially; S. longispinata (Busk, 1884) from the South Atlantic has small, oval avicularia directed laterally or proximolaterally, and large, spatulate avicularia directed distally or distolaterally and medially; S. cardiophora Winston and Jackson, 2021 from Jamaica, has a broader sinus; S. angusta Vieira, Gordon, Souza, and Haddad, 2010 from Brazil, differs in the shape of the orifice which has a less elongate, almost semicircular anter, and the shape of avicularia with narrow, rounded triangular rostra and crossbars without a ligula; S. arborescens Vieira, Gordon, Souza, and Haddad, 2010 , also from Brazil, is characterized by its erect and bilaminar colonies, a shallower orificial sinus, less conspicuous condyles, and avicularian rostra that are narrow and rounded triangular; S. asper (Canu and Bassler, 1923) from the Gulf of Mexico has an orifice with a less elongate anter, shallower and broader sinus, and less developed condyles ( Winston, 2005).