Triphyllozoon angustum, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Triphyllozoon angustum sp. nov.

Di Martino, Rosso, and Taylor

Figure 62 View FIGURE 62

zoobank/ F8FBE39D-5A4E-4966-9652-2F33E524E64F

Type material. Holotype PMC. B73. 29.7.2024 a, sample 19113 ( Figure 62A–D, G–I View FIGURE 62 ); paratype PMC. B73. 29.7.2024 b1, sample 19055 ( Figure 62E–F View FIGURE 62 ); paratype PMC. B73. 29.7.2024 b2, sample 19105 (not figured); paratype PMC. B73. 29.7.2024 b3, sample 19200 (not figured); paratype PMC. B73. 29.7.2024 b4, sample 19094 (not figured); Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Etymology. Latin, meaning narrow, referring to its narrow, bi- to triserial trabeculae.

Diagnosis. Triphyllozoon with elongate fenestrae and bi- to triserial trabeculae; autozooids with sparsely tubercular frontal shield and frontal avicularia of three types: small and subcircular, medium-sized subelliptical/spatulate, and large spatulate; oval suboral avicularium embedded in the proximal peristome, the two lobes fusing and forming a deep teardrop-shaped pseudosinus; two lateral spines present or absent; ovicell projecting frontally from the branch, with trifoliate dentate suture with longer median arm and lateral arms diverging at 160– 180°, curving downward to form a semicircle, central mucro fairly developed; dorsal side sparsely granular with numerous avicularia of the same three types seen on the frontal side, with the medium-sized spatulate being the most common.

Description. Colony erect, rigid, reticulate; fenestrae elongate, c. 3.6 mm long by 0.6 mm wide; trabeculae 340–600 µm wide, consisting of 2–3 alternating autozooidal series. Autozooids flask-shaped, longer than wide (mean ZL/ZW 1.80), with indistinct boundaries; frontal shield slightly convex, sparsely tubercular, with tubercles measuring 12– 30 µm in diameter, imperforate except for a few, small, round to elliptical pores along the lateral margins, 7–20 µm in maximum diameter. Peristome well developed proximally with the two lobes fusing to form a deep (100–130 µm), teardrop-shaped pseudosinus, 20–30 µm in maximum width, slightly off-centre; frequently a small, oval avicularium enclosed on the rim of one lobe, either side, placed transversely and directed laterally (type 1). Secondary orifice eye-shaped with two oral spine bases sometimes present at its lateral corners, also visible in ovicellate zooids, c. 15 µm in diameter at the base. Numerous frontal avicularia present in three types: small, subcircular avicularia usually placed on the proximal portion of the zooid frontal and directed proximolaterally (type 2); medium-sized avicularia, variable in shape from subelliptical with parallel sides to slightly spatulate, usually placed at mid-length or more distally on the zooid, perpendicular or oblique to the zooid axis and directed proximally to proximolaterally (type 3); large spatulate avicularia, usually placed and directed as the medium-sized ones (type 4); each zooid with one or more avicularia in various combinations. On the dorsal side of the colony, all three types (i.e., types 2 to 4) present, with the medium-sized slightly spatulate avicularia being the most frequent. All avicularia with complete crossbar. Ovicell hyperstomial, prominent, projecting frontally from the branch surface with a fairly developed distomedial mucro; ooecium slightly longer than wide (mean OvL/OvW 1.15), initially smooth but becoming sparsely granular as the frontal when covered by secondary calcification, with trifoliate dentate suture, with a longer median arm (85–160 µm) compared to the lateral arms (70–110 µm), diverging at 160–180° and curving downward to form semicircles; width of the suture similar in median and lateral arms (18–39 µm vs 17–33 µm); labellum short and square. Dorsal side sparsely granular like the frontal, with spaced oblique vibices (15–30 µm wide) outlining subrectangular or irregularly polygonal kenozooidal sectors, including a few sparse elliptical and circular marginal pores (19–25 µm in diameter) and numerous avicularia, usually placed around the sector perimeter and randomly directed, of the types described above.

Measurements (µm). ZL 541±30, 505–577 (2, 5); ZW 301±39, 263–352 (2, 5); AvL (type 1, suboral) 41±6, 35–51 (1, 5); AvW (type 1, suboral) 38±5, 30–44 (1, 5); AvL (type 2, frontal) 45±4, 35–50 (4, 16); AvW (type 2, frontal) 46±7, 31–53 (4, 16); AvL (type 3, frontal) 82±11, 66–108 (4, 15); AvW (type 3, frontal) 52±5, 42–62 (4, 15); AvL (type 4, frontal) 177±31, 155–213 (2, 3); AvW (type 4, frontal) 57±23, 40–83 (2, 3); AvL (type 2, dorsal) 43±7, 34– 55 (2, 7); AvW (type 2, dorsal) 39±5, 31–46 (2, 7); AvL (type 3, dorsal) 98±9, 76–113 (3, 20); AvW (type 3, dorsal) 66±8, 51–80 (3, 20); AvL (type 4, dorsal) 220±23, 163–244 (3, 12); AvW (type 4, dorsal) 107±13, 76–123 (3, 12); OvL 301±16, 263– 323 (3, 17); OvW 262±18, 236–298 (3, 17).

Remarks. This species has been closely compared to other bi- to triserial species of Triphyllozoon known to date and is found to be distinct. Triphyllozoon bimunitum (Ortmann, 1890) , T. bimunitum trimunitum (Buchner, 1924) , and T. bimunitum sparsimunitum (Buchner, 1924) all have bicuspid avicularia (Hayward, 2000; Hirose, 2010). Triphyllozoon contortuplicata (Busk, 1884) lacks dorsal avicularia, and its frontal avicularia are nearly suboral and triangular. Triphyllozoon formosoides Hayward, 2004 has avicularia with cusps and a peristome formed by two lateral flaps without a deep pseudosinus. In Triphyllozoon gracile Gordon and d’Hondt, 1997 , avicularia are oval rather than spatulate. Triphyllozoon inornatum Harmer, 1934 has large tricuspid avicularia on the dorsal side and at the fenestrae, and its ovicell is non-mucronate. Triphyllozoon patulum Harmer, 1934 shares spatulate avicularia with the new species but differs in having a non-mucronate ovicell with no strongly curved suture arms and a peristome with a short pseudosinus. Spatulate avicularia and non-mucronate ovicells are also typical of T. punctiligerum (Ortmann, 1890) . Triphyllozoon separatum Harmer, 1934 and T. tuberculiferum Harmer, 1934 have elongate triangular avicularia. Triphyllozoon trifoliatum Harmer, 1934 has a short pseudosinus, and an avicularium associated with the ovicell.