Reteporella phimostoma, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Reteporella phimostoma sp. nov.

Di Martino, Rosso, and Taylor

Figure 57 View FIGURE 57

zoobank.org/ D12C6C7C-9853-4B74-A74F-F720155C3EC0

Type material. Holotype PMC. B71. 29.7.2024 a, sample 19061; Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Etymology. Greek, from the combination of ‘phimos’, meaning muzzle, and ‘stoma’, meaning mouth, referring to its complex peristomial avicularian structure, which resembles a muzzle.

Diagnosis. Reteporella with dichotomously branching, non-fenestrate colony form, with biserial branches, becoming triserial at bifurcations; autozooids with nodular frontal shield; primary orifice obscured by the peristome and the complex peristomial avicularium; peristomial avicularium centrally positioned, parallel to autozooid axis, directed proximally, connected to a skeletal structure continuous with peristomial spines (5–6), defining a circular opening on each side of avicularium; spines coalescent in groups of 2–3; ovicell kenozooidal with median slit-like fenestra in the ectooecium revealing a fully calcified endooecium, sometimes covered by secondary calcification; dorsal side with raised vibices and rounded avicularia.

Description. Colony erect, rigid, non-fenestrate, dichotomously branching with bifurcations occurring at angles of 60–70º; branches generally narrow, biserial, becoming triserial and wider at bifurcations (216–425 µm wide). Autozooids distinct, separated by raised margins, arranged in alternating longitudinal rows, irregularly pentagonal to hexagonal, elongate (mean ZL/ZW 1.89). Frontal shield flat, slightly convex below the orifice, nodular, imperforate except for a single circular pore, placed medially at 25–40 µm from the orifice, with a diameter of 8–12 µm. Primary orifice deep, concealed by a short peristome and the complex structure of the peristomial avicularium; secondary orifice bean-shaped; 5–6 robust oral spine bases in a variable configuration, with those lateral coalescent in groups of two or three, appearing bi- to trifurcated, with the distalmost spine sometimes separated/not coalescent; spine base 12–18 µm in diameter; depending on their original position, 3–4 spines still visible in ovicellate zooids. Peristomial avicularium constantly present, placed medially in respect to the orifice and facing frontally, parallel to autozooid axis, flat or slightly sloping towards the orifice, elliptical, directed proximally, with a complete crossbar and a median trapezoidal denticle on the outer distal margin, connected with a complex skeletal structure to the distolateral spines, forming a sort of muzzle-like structure obscuring the orifice; between this structure and the avicularium are two small, circular openings, one on each side, c. 20 µm in diameter. Frontal avicularia seemingly absent. Ovicell pyriform, elongate (mean OvL/ OvW 1.15), seemingly kenozooidal, modifying the proximal margin of the distal autozooid which is raised and covers the distal periphery of the ooecium; ooecium wrinkled, with a slit-like median fenestra 50–75 µm long, extending from the proximal margin of the ectooecium up to slightly more than half of its total length, narrow, slightly enlarging distally; endooecium fully calcified; labellum absent; secondary calcification gradually covering ooecia making the suture not visible and the surface characterized by raised margins corresponding to the outline of autozooids. Dorsal side nodular, with smooth, raised vibices outlining irregularly kenozooidal polygonal sectors of varying sizes; each sector with one or two sparse circular pores and sometimes a rounded raised avicularium, usually adjacent to the margin of a sector, randomly directed, with a complete crossbar. Secondary calcification patches, likely due to kenozooidal repair, observed on the frontal shield of some zooids.

Measurements (µm). ZL 260±32, 214–295 (1, 9); ZW 138±16, 118–167 (1, 9); AvL (suboral) 41±4, 34–47 (1, 13); AvW (suboral) 28±3, 24–34 (1, 13); AvL (dorsal) 33±3, 31–37 (1, 4); AvW (dorsal) 31±5, 26–36 (1, 4); OvL 113±9, 100–131 (1, 8); OvW 98±8, 88–107 (1, 8).

Remarks. We assigned this species to Reteporella based on several key characters: the presence of peristomial spines, the erect and rigid colony form that can be non-fenestrate, the appearance of the dorsal side of branches with vibices and avicularia, and the shape of the ooecium, which can be completely calcified. However, this species is unique among all identified Reteporella species due to its complex peristomial avicularian structure that forms a continuum with the peristomial spines. In addition to the absence of this feature, Japanese Reteporella species also differ in other characters. Reteporella anatina (Ortmann, 1890) and R. anatina limitata (Ortmann, 1890) have peristomes with two denticles and frequent duckbill-shaped frontal avicularia; R. crenulata (Okada, 1920) has an aperture with serrated proximal margin and three types of frontal avicularia; R. dendroides Ortmann, 1890 has a peristome with a pseudosinus and usually numerous frontal avicularia of two types; R. kinoshitai (Okada, 1920) has a peristomial pseudosinus and three types of frontal avicularia; R. minor Ortmann, 1890 has a peristomial slit-like pseudosinus; R. misakiensis (Okada, 1920) has a fenestrate colony, a slit-like pseudosinus, and bifid suboral avicularia; R. peripherica Ortmann, 1890 has branches with a greater number of autozooids, a pitted frontal shield, a pseudosinus, and frequent frontal avicularia; R. obtecta (Buchner, 1924) has a peristomial avicularium leaning on one side, and a circular pseudosinus on the other; R. terebrata (Buchner, 1924) has a peristomial round pseudosinus and large triangular frontal avicularia; R. watanabei (Okada, 1920) has a fenestrate colony and centrally placed frontal avicularia. The potential new species of Hirose (2010), Reteporella n. sp. 1 and Reteporella n. sp. 2, have several spines but peristomial avicularia defining only a single circular pseudosinus on the opposite side. They also differ in the presence of frontal avicularia.