Fenestrulina communis Rosso & Di Martino 2025, sp. nov.

Fenestrulina communis Rosso & Di Martino sp. nov. Figs 1, 8, 9, 10, 11, 12, 22, 23, 24; Tables 1, 2 Fenestrulina malusii (Audouin): Rosso 1989: tables 3 d, 4 d; Hayward and Ryland 1999: 300, fig. 138 A, B; Hayward and McKinney 2002: 81, fig. 37 A – D; Rosso et al. 2013: table 1; Rosso et al. 2019 a: table 1; Subías-Baratau et al. 2022: table 2, fig. 5 a. Type material. Italy • Holotype large ovicellate colony encrusting a flat and smooth plastic item, with several lobes, including hundreds of ovicellate and non-ovicellate zooids and the ancestrula. Mediterranean, Tyrrhenian Sea, NW Sicily, Magaggiari beach, Cinisi, near Palermo; 38.159651°N, 13.083972°E; stranded on the beach; Dec. 2023; C. Siddiolo leg.; PMC.B 39.23.2.2024.a. Italy • Paratypes 15 colonies, some small, including only the ancestrula and a few periancestrular autozooids, others large, with ovicellate and non-ovicellate autozooids and often the ancestrula, plus five isolated ancestrulae; same details as the holotype; PMC.B 39.23.2.2024.b 1–8 on the same plastic item as the holotype; PMC.B 39.23.2.2024.b 9–15 on a second bent plastic item. Other material examined. Italy • 2 living colonies on plastic. Mediterranean, Tyrrhenian Sea, NE Sicily, Tono beach, Capo Milazzo Peninsula; 38°14'43"N, 15°14'26"E; stranded on the beach; Apr. 2024; A. Rosso & E. Di Martino leg.; PMC Rosso-Collection I.H.B.116.a. Italy • 1 fragmentary colony, Mediterranean, Ionian Sea, SE Sicily, Plemmirio MPA, Granchi submarine cave, sample GR 2; 15°19'40.2"N, 37°01'13.2"E; 20 m depth; Sept. 2009; V. Di Martino leg.; scuba diving • 2 colonies, one on the free valve of the brachiopod Novocrania anomala (Müller, 1776) and one on a fragment of the bryozoan Reteporella elegans Harmelin, 1976. Mediterranean, Ionian Sea, SE Sicily, Plemmirio MPA, Gymnasium submarine cave, sample GY 2; 15°18'48"N, 37°00'12"E; 20 m depth; Sept. 2009; V. Di Martino leg.; scuba diving • 1 fragmentary colony, Mediterranean, Ionian Sea, SE Sicily, Plemmirio MPA, Mazzere submarine cave, sample MZ 1; 15°18'35.6"N, 37°00'18.3"E; 20 m depth; Sept. 2009; V. Di Martino leg.; scuba diving; PMC Rosso-Collection I.H.B.116.b. Italy • few zooids on a shell fragment. Mediterranean, Ionian Sea, SE Sicily, Gulf of Noto, sample PS / 81 CR 1; 36°44'N, 15°10'E; 45 m depth; Jun. 1981; dredge; PMC Rosso-Collection I.H.B.116.e. Italy • 1 colony including the ancestrula and ~ 30 ovicellate and non ovicellate autozooids on a bioclast. Mediterranean, Ionian Sea, SE Sicily, Ciclopi Island MPA, Ciclopi 2000 cruise, sample 20 B; 4145500 N, 513130 E; 50 m depth; Jul. 2000; A. Rosso leg.; dredging; PMC Rosso-Collection I.H.B.116.c. Italy • few zooids on an alga. Mediterranean, Ionian Sea, SE Sicily, Ciclopi Island MPA, off Santa Tecla, sample ST. 1. Z 9; 37°38'17"N, 15°10'53"E; 9 m depth; Jun. 2015; M. Catra & R. Leonardi leg.; scuba diving; PMC Rosso-Collection I.H.B.116.d. Spain • 4 small colonies on three benthic plastic debris. Mediterranean, Liguro-Provençal basin, off Palamós; 41.6°N, 3.4°E; 100 m depth; Dec. 2020; B. Figuerola leg.; trawl; PMC EDM-BF Collection SP.H.B.116.f. Diagnosis. Fenestrulina with large frontal pseudopores, partially occluded by a star-shaped plate formed by spinules slender at pore margins, flattening and merging at the centre. Description. Colony glassy in appearance, encrusting, multiserial, unilaminar, forming large patches up to 1.5 cm 2 on flat and smooth plastic substrates, with an irregularly lobate outline (Fig. 11 A). Interzooidal communications via multiporous septula: two proximolateral (150 μm wide), two distolateral (148–208 μm wide, n = 5) and one distal (31–172 μm wide, n = 4), located at mid-length along lateral and distal walls (Figs 8 B, 9 D, 10 A – C), each comprising a dozen round pores (6–9 μm in diameter) (Fig. 8 I, J). Autozooids large, roughly hexagonal, distinct, contiguous, boundaries marked by narrow, deep grooves, occasionally widening into subtriangular spaces at triple junctions. Lateral walls sub-vertical, slightly exposed at junctions (Fig. 8 C – E). Frontal shield gently marked by a slightly raised rim of smooth calcification lining orifice proximally and laterally, extending distally into long (mean length 148 μm, n = 11) lappets on both sides of the orifice (Fig. 8 D – F, H). Lappets sometimes encircling and merging beyond orifice in irregular zooids (Figs 10 D, G, L, 11 F). Surface gently convex, slightly more raised at ascopore level, smooth; circular pseudopores, ~ 30 per zooid, reduced to 13–16 in periancestrular zooids, increasing to 40 in later autozooids (Fig. 8 A – E), more in teratological forms. Pseudopores mainly in distal half, arranged in two or three rows between orifice and ascopore, one or two lateral rows in distal half, often absent / sparse proximally (Fig. 8 B – E). Pseudopores irregularly subcircular, slightly infundibular, lumen partly occluded by an irregularly spiny, star-shaped calcification process, depressed in relation to frontal surface, formed by 3–5 spinules progressively flattening and merging centrally, tending to obliterate the lumen but often leaving a small round central opening (Figs 8 L, M, 23 C). Two, occasionally one, cryptocystidean areas distally to orifice, between spines, each with 1–3 pseudopores (Figs 8 E, G, H, 10 G, H). Basal wall largely uncalcified. Primary orifice transversely D-shaped, hinge-line straight with two shoulders at proximal corners; distal rim finely denticulated (Fig. 8 F – H). Oral spines usually two, occasionally three, four in periancestrular zooids, ~ 100 μm long (base diameter 15–20 μm), distally positioned, never proximal than to mid-orifice length (Fig. 8 E – H). Ovicellate autozooids with two spines, barely visible in frontal view, lateral to ovicell proximal rim corners. Ascopore centrally placed, ~ 130 μm proximal to orifice, distance often exceeding orifice length (Fig. 8 A – F); situated in a reniform field of smooth gymnocystal calcification marked by a slightly raised rim, often fusing proximally with arched proximal rim of frontal shield in presence of ovicell; lumen large, transversely C-shaped between the distal short and wide tongue and the arched proximal border; rim denticulate, denticles simple or bi- to trifurcated (Fig. 8 C – F), occasionally almost meeting (Fig. 8 K). Ovicell subglobular, prominent, narrowing proximally to fit orifice width, slightly obscuring distal part of orifice, seemingly subcleithral, produced by distal autozooid (Fig. 8 C, D). Endooecium calcified, smooth to gently nodular, faintly ribbed at periphery, rimmed by a row of ~ 15 large, quadrangular pores separated by narrow calcified bridges, giving scalloped appearance; proximal margin on a level with, or just proximal to, proximalmost pair of oral spines, rim slightly folded upwards. Ectooecium reduced to a slightly raised rim of gymnocystal calcification, lining proximal raised edge of distal autozooid. Ancestrula tatiform (Figs 9, 24 C – D), oval but irregularly outlined, smaller than periancestrular autozooids, gymnocyst narrow (60–100 μm wide), more extensive proximally with ten spines, five surrounding orifice, slightly more closely spaced than proximal ones, slightly indenting the raised rim, delimiting the narrower (~ 15 μm), almost smooth cryptocyst. Opesia oval, occupying almost four-fifth of total length (~ 300 μm long by 250 μm wide). Two longitudinally elongated (Fig. 9 A – C) cryptocystidean areas (each with 1 or 2 pores) between the three distalmost spines and the proximalmost ones, one on each side. Ancestrula first showing only one large distal pore-chamber window connecting it to the first budded distal autozooid; budding pattern: one distal, two distolateral, two proximolateral and one, or rarely two, proximal autozooids, totalling six or seven periancestrular autozooids (Fig. 9). Budding loci seemingly produced after resorption (compare Fig. 9 A with Fig. 9 B, C). Ancestrula often regenerating as a miniature autozooid (Fig. 9 F, G). Kenozooids present, usually observed at colony lobe contacts, between neighbouring colonies, and in damaged areas; from very small (~ 80 μm) to large, irregularly shaped, in furrows between autozooids, or similar in size to autozooids, irregularly polygonal in shape (Figs 10 I, K, L, 11 H, I, 12 F), with scattered (Fig. 12 F) or more densely spaced pseudopores (Fig. 10 K, L); the ascopore almost centrally placed, circular to ellipsoidal, evenly denticulated without distal tongue (Fig. 10 L), or C-shaped as in autozooids (Fig. 10 K), or absent (Fig. 10 I). Etymology. From the Latin communis, meaning common, referring to the common / frequent occurrence of this species in multiple samples and localities within the Mediterranean. Remarks. Colonies reported as F. malusii from the British Isles (Hayward and Ryland 1999) and off Rovinj (Croatia) in the northern Adriatic Sea (Hayward and McKinney 2002) resemble F. communis sp. nov., especially in the morphology and location of pseudopores, as well as their stellate calcification processes. Autozooids from the British Isles show two or three oral spines, similar to those in our material from stranded plastic debris, which usually bear two very distally located and closely spaced spines (Fig. 8 E, F). Three spines are observed less frequently (Fig. 8 H), while four spines are exceptional (Fig. 8 G). In contrast, specimens from the northern Adriatic Sea are described as having four oral spines, although most figured specimens show three, except for periancestrular autozooids that have five (Hayward and McKinney 2002: fig. 37 A and D, respectively). Autozooid measurements reported for these populations, especially those from the northern Adriatic, are slightly smaller than those colonising plastic items in Sicily. This reduced size reflects the prevalence of young colonies, mainly composed of periancestrular autozooids and those in the early astogenetic repetition zone. This interpretation is supported by the transition f