Fenestrulina communis Rosso & Di Martino, 2025

Rosso, Antonietta, Di Martino, Emanuela, Donato, Gemma, Figuerola, Blanca, Gerovasileiou, Vasilis, Siddiolo, Chiara, Sinagra, Alessandro, Sanfilippo, Rossana & Sciuto, Francesco, 2025, Unlocking Mediterranean bryozoan diversity: seven new species unveiled after fixing a neotype for Fenestrulina malusii (Audouin & Savigny, 1826) (Cheilostomatida, Fenestrulinidae), ZooKeys 1254, pp. 1-74 : 1-74

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 from four to three oral spines shown in Hayward and McKinney (2002: fig. 37 A). Similarly, relatively small autozooids have been documented in colonies from eastern Sicily (Ionian Sea), collected in submarine caves of the Plemmirio MPA ( Rosso et al. 2013) or associated with infralittoral algae and circalittoral detritic bottoms at Ciclopi Islands MPA ( Rosso et al. 2014, 2019 a). These autozooids, however, have two or three oral spines. Unlike the type material, lateral pseudopores in some autozooids, particularly those from submarine caves, tend to develop near or along the marginal elevated rim of the frontal shield.

Additional colonies from unspecified Mediterranean localities may also belong to this species. This includes a colony housed at NHMUK, figured by Wasson and De Blauwe (2014: fig. 4), as well as the specimen figured by Zabala and Madurell in GBIF (2024). In contrast, the colony from Chios Island ( Aegean Sea, Greece), identified as F. malusii s. s. by Gordon (1984), differs in several respects, including a rugose to crested ovicell, more infundibular frontal pseudopores partially occluded by radial denticles that only occasionally meet at the centre, and a shorter distance between the orifice and the ascopore. This morphotype may represent a distinct species, but additional material is required to confirm its taxonomic identity.

Fenestrulina communis sp. nov. is also similar to F. inesae Souto, Reverter-Gil & Fernandez-Pulpeiro, 2010 a from off Algarve (southern Portugal, Atlantic Ocean), mainly in the stellate appearance of its frontal pseudopores. However, F. inesae has ~ 60 frontal pseudopores, far exceeding the 18–40 observed in F. communis sp. nov. Its pseudopores are also significantly smaller in diameter (25 μm vs 31–45 μm). Furthermore, in F. inesae , autozooids are slightly shorter (595 vs 646 μm), orifices are longer and comparably more elongate (144 × 160 μm; OL / OW: 0.90 vs 123 × 176 μm; OL / OW: 0.70), ovicells are distinctly shorter and wider than long, unlike the almost isodiametric ones visible in F. communis sp. nov. (250 × 323 μm vs 359 × 338 μm), and the ascopore is significantly smaller and longer than wider (89 × 59 vs 74 × 113 μm).

Fenestrulina communis sp. nov. shows high variability in autozooid shape and size. Some are highly elongate (Fig. 10 A ), others notably widened (Fig. 10 A, B, D ), with widths nearly matching two contiguous autozooids. Some enlarged forms likely result from the fusion of initially separated buds (Fig. 10 C ). The shape also varies from elongate hexagonal / ovoidal to highly irregular (Fig. 10 C, D ), with some morphologies seemingly adapted to fill gaps between colonies at contact zones or in damaged colony portions (Figs 10 G , 11 B, D, E, I ). Indeed, colonies densely encrusted the plastic substrate, with at least nine colonies (including two juveniles) counted on ~ 4 cm 2, plus additional detached colonies, as indicated by their left traces (Fig. 11 A ). Interestingly, at colony encounter edges, overgrowth was rarely observed, with irregularly shaped kenozooids forming only in a few cases (e. g., Fig. 10 K ). More commonly, colonies apparently fused, with autozooids at contact points modified to maximise the encrustation of the available substrate without overgrowing each other. We observed colonies with autozooids: 1) curving and deflecting from their original direction to merge and continue growing alongside (Fig. 11 B – F ); 2) apparently fusing to form larger ‘ double’ autozooids with two widely spaced ascopores, none aligned with the orifice (e. g., Fig. 10 G ); 3) irregularly shaped along boundaries, some with prominences or cauda-like extensions to connect with autozooids from another colony (Fig. 11 B – F ). Three similar homosyndrome cases were reported in California for colonies of putative F. malusii encrusting Macrocystis pyrifera (Linnaeus) C. Agardh and Agarum fimbriatum Harvey at 5–25 m depth off Santa Catalina Island, and anthropogenic substrates at the Marine Science Center ( Nielsen 1981). There, colony fusion involved ovicell formation, with an autozooid from one colony induced by a maternal zooid from another via its distal pore chamber ( Nielsen 1981: fig. 21 A, B). The interacting colonies were similar in size and possibly genetically related ( Nielsen 1981). Due to the detachment of large colony portions, the full size of interacting colonies in our material remains uncertain. However, their occurrence on the same drift plastic item suggests they originated from one or few pioneer colonies, whose offspring settled nearby.

Interactions between F. communis sp. nov. colonies and other bryozoan species were also observed, including an undetermined cyclostome and Aetea (Fig. 12 A – D ). In both instances, Fenestrulina colonies overgrew the encrusting skeletal portions of the competitors without obliterating the zooidal openings but only encircling the peristomes (Fig. 12 D ) and the erect zooidal tubes of Aetea (Fig. 12 B, C ), sometimes deforming their own autozooids (Fig. 12 C ). Some colonies also interacted with young anomiid bivalves, either overgrowing them (Fig. 12 E, F ) or ceasing growth at a short distance (Fig. 11 A – D ), displaying a stand-off behaviour ( Taylor and Wilson 2003).

Numerous autozooids show regeneration, often by intramural budding, producing new orifices, partial frontal shields (Fig. 10 I, J ), entire new autozooids (Fig. 10 B ), occasionally with reverse polarity (Fig. 10 B, J ), and kenozooids (Fig. 12 F ). Closure plates occluding orifices are also common. They resemble the frontal shield, including pseudopores (Fig. 10 H, I ), and sometimes an ascopore (e. g., Fig. 10 F ). An ovicell lacking its ectooecium was also observed (Fig. 10 F ).

Habitat distribution.

Fenestrulina communis sp. nov. occurs in relatively shaded shelf habitats, ranging from semidark and dark submarine caves at ~ 20 m depth to deeper ( 50 m) coarse detritic bottoms swept by currents. Colonies studied by Hayward and McKinney (2002) from near Rovinj, though not explicitly stated, likely originated from alga / plant-rich habitats at less than 40 m depth. The species has also been found at shallower depths ( 9 m) in the Infralittoral Algae biocoenosis, but is also capable of thriving in well-lit conditions, as evidenced by its settlement and growth on drift plastic items, the source of most studied colonies. Additionally, colonies have been found on benthic plastic items collected at 100 m depth off Catalonia. The colonisation likely occurred while the plastic was still buoyant and floating in shallower waters, before the accumulated encrustation increased its weight, eventually causing it to sink to the seafloor ( Subías-Baratau et al. 2022).

Geographical distribution.

Fenestrulina communis sp. nov. is an Atlanto-Mediterranean species. Its distribution appears to be centred around the British Isles in the Atlantic ( Hayward and Ryland 1999), and extends across the Mediterranean, with records from the western Ionian Sea and the Tyrrhenian Sea off the Italian coast, as well as the northern Adriatic Sea off Croatia ( Hayward and McKinney 2002). The species’ ability to encrust floating objects, including anthropogenic debris, suggests its opportunistic behaviour and may facilitate its wide distribution across the western Mediterranean, including the Catalan region and the southwestern Tyrrhenian Sea. However, it is plausible that the species also occurs in natural habitats in these areas, as they fall within its known distributional range. Fenestrulina communis sp. nov. seems to align with the modern to contemporary concept of F. malusii , as demonstrated by the number of synonymies proposed in relation to the limited literature illustrating Fenestrulina colonies. Consequently, a thorough revision of existing collections with colonies identified as F. malusii from additional sites across the western Mediterranean would likely reveal that they belong to this species rather than F. malusii .

Figures

Figure 1. Geographical distribution of Mediterranean Fenestrulina species (and specimens) examined in this study. Asterisks denote newly described species and the only confirmed record of Fenestrulina malusii (Audouin & Savigny, 1826), illustrated here with Savigny’s original drawing (reproduced from d’Hondt 2006) shown on the left. Type material is shown for each species, except for F. malusii, for which the neotype (upper image) and a colony fragment from Ile-Rousse Bank, NW Corsica (lower image) are figured. Large symbols indicate type localities; small symbols mark additional occurrences. Symbol colours correspond to species as follows: red = F. malusii; bright green = F. cavernicola sp. nov.; vivid pink = F. communis sp. nov.; pale blue = F. foveolata sp. nov.; blue = F. granulosa sp. nov.; olive green = F. kalliste sp. nov.; dark green = F. ovata sp. nov.; purple = F. variorugosa sp. nov.; lilac = Fenestrulina sp. Note: in areas with multiple records, only one symbol is used to represent the locality.

Figure 8. Fenestrulina communis Rosso & Di Martino, sp. nov. from a plastic item stranded on Magaggiari beach, Cinisi (Palermo), NW Sicily, Tyrrhenian Sea. A, C, D. Paratype PMC. B 43.23. 2.2024. b 8; B, F, G, K. Holotype PMC. B 39.23. 2.2024. a; E, H, I. Paratype PMC. B 39.23. 2.2024. b 9; J, L, M. Paratype PMC. B 39.23. 2.2024. b 10. A. General view of a colony portion showing common ovicellate autozooids; B. Non-ovicellate autozooids regularly arranged near the colony margin; C. Non-ovicellate autozooids, some distal to ovicells, illustrating morphological variation; D. Ovicells with moderately tuberculate surfaces and scalloped distal rims; E. Non-ovicellate autozooid; F. Autozooid with two oral spines placed very distally and semicircular orifice; G, H. Close-up of two orifices with four and three spines, respectively. Note the arched distal rim with few faint denticles and the straight proximal rim with shouldered corners; I, J. Multiporous septula seen externally (I) and internally (J) along lateral and distal walls; K. Ascopore with some denticles merging; L, M. Frontal pseudopores showing different degrees of development of the stellate process. Note that few pseudopores are present in the proximal frontal shields in panels A – F. Scale bars: 1 mm (A); 500 μm (B, C); 200 μm (D, E); 100 μm (F – K); 50 μm (L, M).

Figure 9. Fenestrulina communis Rosso & Di Martino, sp. nov. tatiform ancestrula and periancestrular autozooids from a plastic item stranded on Magaggiari beach, Cinisi (Palermo), NW Sicily, Tyrrhenian Sea. A. Paratype PMC. B 43.23. 2.2024. b. 16; B. Paratype PMC. B 39.23. 2.2024. b. 17; C. Paratype PMC. B 39.23. 2.2024. b. 10; D. Paratype PMC. B 39.23. 2.2024. b. 1; E. Paratype PMC. B 39.23. 2.2024. b. 8; F, G. Holotype PMC. B 39.23. 2.2024. a. A. Recently metamorphosed ancestrula with only the distal pore chamber. Note the ten long spines and cryptocystidean areas between oral spines (arrowed); B. Ancestrula budding the first distal autozooid, showing two distolateral budding loci, possibly formed after a resorption process; C. Close-up of the ancestrula of an asymmetrical young colony with four zooids. The ancestrula shows one distal and one proximal budding locus on one side. Note the large lumina of some incompletely formed pseudopores in periancestrular autozooids; D. Another asymmetrical young colony, apparently ceasing growth near an adult conspecific colony; E. Tatiform ancestrula typically surrounded by six periancestrular autozooids; F, G. Periancestrular area of the holotype (F) and a detail of the ancestrula (G), regenerated as a miniature autozooid with a central ascopore. Scale bars: 200 μm (A – D, G); 500 μm (E, F).

Figure 10. Fenestrulina communis Rosso & Di Martino, sp. nov. kenozooids and teratologies from a plastic item stranded on Magaggiari beach, Cinisi (Palermo), NW Sicily, Tyrrhenian Sea. A – D, F, G, K, L. Holotype PMC. B 39.23. 2.2024. a; E. Paratype PMC. B 39.23. 2.2024. b 9; H. Paratype PMC. B 39.23. 2.2024. b 2; I. Paratype PMC. B 39.23. 2.2024. b 7 a; J. Paratype PMC. B 39.23. 2.2024. b 8. A. Wide and slender autozooids; B. Enlarged autozooid at colony margin, placed distally to an autozooid with reversed polarity; C. Large peripheral autozooids, one possibly resulting from fusion of two neighbouring zooids (asterisk); D. Group of autozooids, two showing aberrant morphology (asterisks); E. Aberrant autozooids at the contact zone between adjacent colonies; F. Ovicell lacking the ectooecium and orifice with a closure plate in a non-functional autozooid; G. Irregularly-shaped autozooid with a single orifice and two ascopores, possibly owing to fusion of two autozooids; H. Damaged autozooid showing the orifice with a pseudoporous closure plate; I. Regenerated autozooids and a small, evenly pseudoporous kenozooid (arrowed); J. Regenerated autozooids, including one with reversed polarity; K. Two overgrowing kenozooids with C-shaped ascopores and pseudoporous frontal shields; L. Kenozooid with an evenly pseudoporous frontal shield and a circular ascopore. Scale bars: 500 μm (A – D, I); 200 μm (E – H, J – L).

Figure 11. Fenestrulina communis Rosso & Di Martino, sp. nov. intraspecific interactions and contact zones between adjacent colonies from a plastic item stranded on Magaggiari beach, Cinisi (Palermo), NW Sicily, Tyrrhenian Sea. Holotype PMC. B 39.23. 2.2024. a, and paratypes PMC. B 39.23. 2.2024. b 2 and PMC. B 39.23. 2.2024. b 7 a, b. A. Fragment of the plastic item colonized by F. communis sp. nov. showing the lobate holotype extending from the central part of the white frame to the central part of the black frame, surrounded by some paratypes (1–7); B. Enlargement of the black-framed portion in panel A showing the contact between the holotype and paratype b 2; C. Autozooid (white asterisk in panel B) with lateral prominences, possibly marking the homosyndrome between the holotype and paratype b 2; D. Enlargement of the white-framed portion in panel A showing the contact between the holotype and paratype 7 a, and the stand-off between paratypes 7 a and 7 b near an anomiid bivalve; E, F. Progressively enlarged views of the contact zone in panel B (black asterisk), highlighting a caudate autozooid to the left of the zooid with asterisk. Note the cryptocystidean areas encircling the orifices in some zooids; G. Enlargements of the upper contact area in panel D, showing an enlarged autozooid with a zigzag-shaped, expanded caudal region; H. Enlargement of the lower contact zone in panel D, showing a close-up of an autozooid with two ascopores, indicating fusion of the two colonies. A kenozooid with an elliptical ascopore is also visible; I. Enlargement of the area immediately above the anomiid bivalve in panel D, showing deflecting zooids at the contact zone between paratypes 7 a and b. Scale bars: 1 cm (A); 2 mm (B); 500 μm (C – E, G, I); 1 mm (F, H).

Figure 12. Fenestrulina communis Rosso & Di Martino, sp. nov. inter- and intraspecific interactions from a plastic item stranded on Magaggiari beach, Cinisi (Palermo), NW Sicily, Tyrrhenian Sea. Holotype PMC. B 39.23. 2.2024. a, and paratypes PMC. B 39.23. 2.2024. b 6 and PMC. B 439.23. 2.2024. b 9. A. Paratype b 9 intergrowing with an Aetea colony; B. Enlargement of the white-framed area in panel A showing deformed autozooids and interzooidal spaces filled with a cluster of small kenozooids lacking ascopores. One erect tube of Aetea passes between contiguous Fenestrulina autozooids; C. Enlargement of the black-framed area in panel A showing a deformed Fenestrulina autozooid encircling an erect portion of Aetea; D. Colonies overgrowing an encrusting, unidentified cyclostome whose peristome openings remain unobstructed (arrowed); E. Contact zone between the holotype (bottom) and paratype b 6, both overgrowing an anomiid bivalve (left); F. Enlargement of the black-framed area in panel E showing a possible homosyndrome marked by the fusion of two autozooids (white asterisk), a damaged autozooid regenerated as an irregularly elongated kenozooid with an ascopore (black asterisk) and a second small kenozooid (arrow), both connecting the two colonies, the latter elevating on the opposite lobe. A kenozooid with a median ascopore is also visible. Scale bars: 2 mm (A); 500 μm (B – D, F); 1 mm (E).

Figure 22. Geographical distribution of all known records of Fenestrulina in the Mediterranean, plotted against current summer Sea-Surface Temperatures (data from IFREMER-LOPS Data Visualization Portal https://syntool.ifremer.fr/, accessed Sept. 2024). An asterisk marks the probable origin of the original material of F. malusii. Large dots: collection sites of specimens with confirmed species attribution; small dots: records of putative F. malusii requiring taxonomic revision, but with known provenance; open ellipses: sites, covered by dedicated monographs, from which Fenestrulina species are absent.

Figure 23. Comparison of pseudopores in the studied species of Fenestrulina. A. F. malusii; B. F. cavernicola sp. nov.; C. F. communis sp. nov.; D. F. foveolata sp. nov.; E. F. granulosa sp. nov.; F. F. kalliste sp. nov.; G. F. ovata sp. nov.; H. F. variorugosa sp. nov.; I. Fenestrulina sp. Scale bars: 100 μm.

Figure 24. Comparison of ancestrulae in the studied species of Fenestrulina. A. F. malusii, tatiform; B. F. cavernicola sp. nov., regenerated as a kenozooid; C. F. communis sp. nov., tatiform; D. F. communis sp. nov., regenerated as a miniature autozooid; E. F. foveolata sp. nov., tatiform; F, G. F. variorugosa sp. nov., tatiform. Scale bars: 200 μm.