Pomocellaria spatulata, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Pomocellaria spatulata sp. nov.

Di Martino, Rosso and Taylor

Figure 13 View FIGURE 13

zoobank.org/ F77AB514-8076-4EE1-A7B7-5DB21424592D

Type material. Holotype PMC. B48. 29.7.2024 a, sample 19032; Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Etymology. Latin, meaning spatula-like (i.e., broad and flat), referring to the shape of the dimorphic lateral avicularium.

Diagnosis. Pomocellaria with rounded rectangular autozooids, smooth extensive proximal gymnocyst, negligible smooth cryptocyst bordering the proximal margin of opesia; elliptical to pear-shaped opesia with one inner and two outer distolateral spines, also visible in ovicellate zooids; scutum attachment base located on the inner side at approximately half opesia length; frontal avicularium single or absent, small, drop-shaped, directed distolaterally; lateral avicularium dimorphic, either medium-sized triangular with a hooked rostrum or giant and spatulate with duckbill-shaped rostrum; ovicells with an upside-down, drop-shaped medioproximal fenestra.

Description. Colony erect with narrow (330–390 µm) branches; branches rectilinear, biserial, flat, elliptical in cross-section; articulating nodes or bifurcations not observed. Autozooids distinct, separated by shallow grooves, rounded rectangular, elongate (mean ZL/ZW 2.18), arranged alternately in two longitudinal series. Proximal gymnocyst smooth, extensive; cryptocyst smooth, negligible, bordering the proximal margin of the opesia. Opesia elliptical to pear-shaped, occupying approximately half of the frontal surface (mean OpL/ZL 0.49); a single spine on the inner and two on the outer distolateral corners, 13–22 µm in diameter at the base; spines also visible in ovicellate zooids. Scutum detached, originating laterally from the inner side, attached at about half the length of the opesia, with an attachment base measuring 50–60 µm in maximum diameter. Adventitious avicularia occurring both frontally and laterally. Frontal avicularium often absent; a single damaged example observed, small, drop-shaped with an acutely triangular rostrum directed distolaterally outwards, associated with an ovicell and displaced towards the branch midline, projecting into the inner distolateral corner of the opesia of the adjacent autozooid. Lateral avicularium consistently present in two forms: type 1, a medium-sized triangular type with an upward hooked rostrum tip directed laterally, atop a conical cystid 115–140 µm long; type 2, an enlarged spatulate type with duckbill-shaped rostrum with an undulate margin, facing obliquely and sloping towards the front of the branch while raised towards the back, with a narrow, 8-shaped opening, positioned atop a fan-shaped cystid 190–205 µm long; crossbar seemingly absent in all avicularia types. Ovicells globular, occupying the entire proximal gymnocyst of the distal zooid; ooecium smooth with an almost completely calcified ectooecium, featuring a small, elliptical fenestra with a upside-down drop-shaped, external outline, 70–80 µm long by 35–60 µm wide, located medioproximally, exposing the endooecium. Dorsal side occupied by sac-shaped vibracula with a long, obliquely placed, straight, deep setal groove, and a sinuous median furrow; each vibraculum with a large, circular radicular pore measuring 35–45 µm in diameter, located proximally on the outer side of the branch.

Measurements (µm). ZL 414±14, 397–428 (1, 7); ZW 189±17, 170–226 (1, 7); OpL 201±15, 180– 218 (1, 8); OpW 127±6, 119–135 (1, 8); GymL 199±7, 193–208 (1, 4); CryL 15±5, 9–21 (1, 8); AvL (lateral type 1) 86±15, 67–108 (1, 5); AvL (lateral type 2) 150±38, 123–177 (1, 2); AvW (lateral type 2, proximally) 76±1, 75–77 (1, 2); AvW (lateral type 2, spatulate rostrum) 118±10, 111–125 (1, 2); AvL (frontal) 69 (1, 1); AvW (frontal) 33 (1, 1); OvL 204±1, 203–205 (1, 2); OvW 203±33, 180–227 (1, 2); VibrL 184±13, 67–97 (1, 4); VibrW 86±13, 67– 97 (1, 4).

Remarks. The genus Pomocellaria was introduced by Vieira et al. (2014) for Scrupocellaria -like species with an opesia occupying half the length of the zooid, a reduced cryptocyst, dimorphic lateral avicularia, a single frontal fenestra in the ooecium, and vibracula with a straight setal groove. They assigned five species from the NE Pacific to their new genus. This new species extends the known range of Pomocellaria to the NW Pacific. The spatulate shape of the giant dimorphic lateral avicularium distinguishes this species from other known Pomocellaria species.

Among Scrupocellaria species of uncertain classification, i.e., not yet reassigned to a genus following Vieira et al. (2014), there is one species recorded from Japan, Scrupocellaria muricata (Lamouroux, 1816) . According to Tilbrook and Vieira (2012), who examined specimens from Japan housed at the Museum national d’Histoire naturelle (MNHN) in Paris, and identified by Lamouroux himself as Crisia muricata , this species can be assigned to a complex of species belonging to the genus Tricellaria , characterised by the absence of basal vibracula.