taxonID	type	description	language	source
EB228790FF96FFDC45D4F9D6B09A0DC7.taxon	description	(Figs 2, 7 – 10) ZooBank registration LSID: urn: lsid: zoobank. org: act: FE 18 BFC 7 - F 25 F- 434 F-A 2 E 1 - 3 F 3898258 E 27 Diagnosis: A very large Lirapex, ≤ 7.6 mm SD; shell sculpture of weak, irregularly spaced, intermittent axial ribs. The final whorl expands more rapidly than previous whorls, with the last 0.25 whorls exhibiting loosening of coiling, leading to the adult aperture detaching slightly from the previous whorls. The opercular attachment is surrounded by 22 – 26 short epipodial tentacles. Central tooth with smooth cutting edge. Etymology: From Pantagruel, son of the giant Gargantua in the French writer François Rabelais’ novel series The Five Books of the Lives and Deeds of Gargantua and Pantagruel (Les Cinq livres des faits et dits de Gargantua et Pantagruel) (Rabelais 1534). This species is the largest of all known Lirapex species, hence the name of a giant is fitting. Used as a noun in apposition. Type locality: On black smoker chimneys of Falkor EMARK hydrothermal vent field (23.47 ° N, 44.99 ° W; 3993 m deep) located on the south intersection of the MAR axis with the Kane Fracture Zone (Fig. 2 D – F). Type material: Holotype (MNHN-IM- 2000 - 39946), SD 7.5 mm, SH 6.9 mm, 95 % ethanol (Fig. 7 A), on a black smoker chimney of Falkor EMARK vent field (23.4735 ° N, 44.9866 ° W; 3993 m deep), sampled using the suction sampler of the ROV SuBastian during dive # 495 on-board R / V Falkor (too), cruise FKt 230303, 23 March 2023. Paratype 1 (SMF 380303), SD 7.6 mm, SH 7.5 mm, 95 % ethanol (Fig. 7 D). Paratype 2 (NSMT-Mo 79608), SD 6.5 mm, SH 6.1 mm, 95 % ethanol (Fig. 7 B). Paratype 3 (MNHN-IM- 2000 - 39947), SD 7.2 mm, SH 7.8 mm, 95 % ethanol (Fig. 7 C). Paratype 4 (SMF 380304), SD 7.5 mm, SH 7.3 mm, 95 % ethanol. Paratype 5 (NSMT-Mo 79609), SD 6.2 mm, SH 7.0 mm, 95 % ethanol. Paratype 6 (SMF 380305), SD 7.3 mm, SH 6.8 mm, 10 % formalin; female specimen decalcified for examination of external anatomy. Paratype 7 (SMF 380306), SD 7.0 mm, SH 6.4 mm, 10 % formalin (Fig. 10); male specimen decalcified and used for µ-CT scanning. Paratype lot 8 (SMF 380307), three specimens, 95 % ethanol. Paratype lot 9 (NSMT-Mo 79610), three specimens, 95 % ethanol. Paratype lot 10 (MNHN-IM- 2000 - 39948), three specimens, 95 % ethanol. Description: The shell (Fig. 7) is solid, skeneiform, and very large for the genus (≤ 7.6 mm in diameter). Adult shells consist of 3.5 – 4 whorls, white in colour. Tightly coiled with deep suture, the coiling abruptly loosens in the final 0.25 whorls, leading to the slight detachment of the adult aperture from the previous whorl. The last adult body whorl also expands more rapidly than the previous whorls. The spire height is rather variable among individuals, and some individuals appear to be depressed (Fig. 7 D). Cross-section of the whorls almost round, although a little irregular. The aperture is weakly opisthocline and not significantly thickened. Umbilicus narrow, usually filled by sulphide mineral deposits. Shell sculpture on the teleoconch consisting of weak, irregular axial ribs that are typically stronger on the earlier whorls. Each rib is more often than not intermittent, taking the appearance of dotted lines. The strength of sculpture varies among individuals. Protoconch (Fig. 8 A) about half a whorl and 200 µm in length. The protoconch is sculptured with five very strong, angular spiral ribs, with some weak, irregular axial sculpture between them. This sculpture disappears about halfway through the protoconch, and the distal half is entirely smooth. Teleoconch shell microstructure (Fig. 8 B) of two distinct layers above the myostracum, including a thick cross-lamellar layer on the inner side and a much thinner granular layer outside of it. Shell pores are frequent on the cross-lamellar layer but do not penetrate into the granular layer. The periostracum is thin, semi-transparent, and greenish. A layer of reddish to blackish sulphide mineral deposit typically overlays the periostracum (Figs 7 D, 8 B). The operculum (Fig. 8 C) is multispiral, comprising> 20 volutions in adult snails. It is thin, film-like, and semi-transparent; the colour is yellowish. The edge is free and detached, extending over the next volution to form a fringe. The central part of the operculum is often covered in a thick layer of tablet-like mineral deposit (Fig. 7 C, D). The radula (Fig. 8 D, E) is rhipidoglossate, with a formula of ~ 50 + 4 + 1 + 4 + 50 ~. The rachidian tooth is solid, rigid, and well reinforced. The shaft of the rachidian is triangular, with a triangular overhanging cusp lacking serrations. The three inner laterals are also solid and rigid, similar in shape, with bifurcating reinforcement near the base. The cusp of the innermost lateral is smooth, the second lateral is very weakly serrated, and the third lateral carries relatively stronger serrations. The fourth, outermost lateral is much broader in comparison to the rest and carries clear serrations on the cusp. The laterals each exhibit a minor protuberance on the shaft, near the base. The marginal teeth are long and thin, tapering distally; the size of marginal teeth decreases outwards. The inner marginals have wider, triangular, rake-like cusps that are serrated, forming ~ 12 denticles. The outer marginals have smaller, hook-like cusps that are serrated into fine denticles. The soft parts (Fig. 9) are overall typical of the genus Lirapex. The head is large and without pigmented eyes. The animal is gonochoristic and lacking external sexual dimorphism; the cephalic tentacles are not modified into copulation organs in both sexes. The snout is short, flattened, with the mouth opening ventrally. A pair of thin, film-like jaws are present. The cephalic tentacles are smooth, conical, and gradually decreasing in size distally; the tentacles are ~ 1.5 times as long as the snout when contracted. Both cephalic lappets and neck lobes are lacking. The mantle edge is smooth and lacks tentacles. The columellar muscle extends only ~ 0.3 whorls behind the mantle edge, with the right shell muscle being larger than the left shell muscle. The two shell muscles are connected by a thick band of ventral muscular tissue. The foot is well developed, with a distinct transverse furrow separating the propodium from the mesopodium. Underneath the operculum, the opercular attachment is surrounded by ~ 22 – 26 short epipodial tentacles arranged in a semi-circular fashion around the posterior two-thirds of the opercular attachment. The epipodial tentacles are longest near the posterior edge of the opercular attachment. A 3 D reconstruction of the major organs is shown in Figure 10. Calculations of the organ volumes resulting from the reconstruction are listed in Table 1; the 3 D model is available in an interactive PDF file (Supporting Information, Supplementary Material 3) and as a rotating video rendering (Supporting Information, Supplementary Material 4). The mantle cavity extends ~ 0.5 whorls from the mantle edge, mainly occupied by a sizeable ctenidium on the left occupying 13.72 % of body volume in the specimen measured (Figs 9 C, 10 A). The bipectinate gill carries ~ 60 pairs of gill leaflets. The ctenidium is connected to the left body wall in the posterior two-thirds, and the osphradium is present as a weakly raised and pigmented band underneath the ctenidium. The efferent pallial vein runs parallel and immediately dorsal to the left shell muscle (Fig. 9 G), posteriorly connecting to the pericardium. The pericardium (Figs 9 D, 10 D) contains a monotocardian heart, with the ventricle situated posteroventral to the auricle; it is not penetrated by the intestine. The ventricle occupies 0.43 % of the body volume and the auricle 0.99 % in the specimen measured (Table 1), the ventricle is weakly muscular. The left kidney (nephridium) is situated dorsal to the pericardium and is sizeable. The digestive tract (Figs 9 E, 10 E) is typical of Lirapex species. The radula ribbon is well sized and supported by a pair of cartilages that contact each other in the anterior two-thirds; a pair of salivary glands is situated above the radula ribbon (Fig. 10 B). The oesophagus runs directly towards the posterior to reach the stomach, situated about one whorl posterior to the mantle edge. The first half of the oesophagus is annexed with a small oesophageal gland that occupies 0.36 % of the body volume in the specimen examined (Table 1). The stomach is rather large and connected to the digestive gland by a series of tubular openings (Fig. 10 E). The digestive gland is light grey in colour and fills much of the dorsal part of the visceral mass (Fig. 9). The intestine is long, emerging from the stomach on the left side, and initally runs anteriorly to reach the radula, then abruptly turns back to posterior-left of the stomach, where is loops twice between the stomach and the nephridium (visible from external anatomy, Fig. 9 E). Then it emerges as the rectum immediately to the right of the nephridium (Fig. 10 F) and runs along the mantle roof towards the anterior-right side of the pallial cavity, where it ends in the anus. Much of the stomach and the intestine were filled with organic material mixed with dark, shiny mineral particles. The oesophagus was empty. The gonad is very voluminous, occupying the ventral part of the entire visceral mass (Fig. 10) and taking up 15.20 % of the body volume in the male specimen examined using μ-CT (Table 1). In males, the prostate is present as a series of complexly folded ducts with a lobulated appearance, situated immediately to the right of the rectum. In females, the ovary is of a similar size to the testis, but there is no similar complex glandular structure in the same relative location of the prostate, and the space is instead taken up by the ovary itself. The gonopore in both sexes opens on the right side of the mantle roof. Distribution: Known only from EMARK vent field on the MAR at 3993 m depth (Fig. 1), forming dense colonies on black smoker chimneys (Fig. 2 F). Remarks: The coiled, skeneiform shell combined with a protoconch carrying distinct spiral ridges support the placement of L. pantagruel in Lirapex, alongside anatomical characters such as the two coils of the intestine visible from the external anatomy and the presence of epipodial tentacles only around the opercular attachment (Warén and Bouchet 1993, Chen et al. 2021). Although the anatomy of L. pantagruel does not deviate from typical members of the genus and its radular characters are very similar to those of L. politus (Chen et al. 2017 b), its shell characters are clearly distinct from all other known Lirapex species. The only species with sculpture similar to the intermittent, weak axial ribs of L. pantagruel is L. humatus from the East Pacific Rise, but the shell of L. humatus is more loosely coiled, and the aperture usually detaches more significantly from the previous whorl (Warén and Bouchet 1993). The size of L. pantagruel is also much larger, at a maximum of 7.6 mm, in comparison to 3.4 mm in L. humatus. The only other Atlantic species, L. costellatus, has much broader, denser axial ribs when present and again a smaller, more loosely coiled shell (Warén and Bouchet 2001). The protoconch of L. pantagruel (200 µm) is also much smaller than that of L. costellatus (250 µm). Genetic support Our consensus tree from phylogenetic reconstruction using Bayesian inference (Fig. 11) recovered a strongly supported [Bayesian posterior probability (BPP) =. 96], monophyletic genus Peltospira containing all four species included: P. operculata, P. delicata, P. smaragdina, and P. gargantua. Within Peltospira, P. gargantua was fully supported (BPP = 1) as being sister to P. smaragdina; this pair was, in turn, most closely related to the P. operculata and P. delicata pair, which was moderately supported (BPP =. 86). The genus Peltospira was recovered as being closest to a clade comprising Rhynchopelta and Nodopelta, although the support for this was weak (BPP <. 6). The tree also shows that sequences from both Hydra and Falkor EMARK vent fields, in addition to the pelagic larval stages collected at Hydra, all belong to the same species-level clade of P. gargantua. Lirapex was also recovered as a monophyletic genus including all three species with COI barcode available: L. politus, L. felix, and L. pantagruel. However, the support for this was weak (BPP <. 6). Within Lirapex, L. pantagruel was fully supported (BPP = 1) as the sister species of L. politus. Lirapex was recovered as sister to Pachydermia, with the two genera forming a strongly supported (BPP =. 95) clade. Our consensus tree also recovered the order Neomphalida as a fully supported clade (BPP = 1). The family Melanodrymiidae was also found to be monophyletic, although with only weak support (BPP =. 62). Neomphalidae was found to be a fully supported (BPP = 1) clade, but it was nested within Peltospiridae, rendering the latter paraphyletic. All neomphaline genera with multiple species included in the tree were recovered as monophyletic clades, although the support value varied from weak to strong (BPP =. 66 – 1). Pairwise interspecific K 2 P genetic distances of COI between pairs of the four Peltospira species with genetic data (Table 2) averaged 15.0 % (range 9.4 % – 18.0 %). Meanwhile, the average intraspecific genetic distance was 0.3 % (0.0 % – 0.5 %), revealing a clear barcoding gap. In line with the phylogenetic reconstruction, P. gargantua was found to be closest to P. smaragdina, with an average K 2 P distance of 9.5 %; the average distance from P. operculata was 17.4 % and from P. delicata 16.0 %. Likewise, the pairwise interspecific K 2 P distance between pairs of the three Lirapex species averaged 15.9 % (range 9.3 % – 20.0 %), showing a clear barcoding gap with the interspecific mean of 0.4 % (range 0.0 % – 0.7 %). As in the tree, L. pantagruel was closest to L. politus, with an average K 2 P distance of 9.3 % (range 9.1 % – 9.5 %).	en	Chen, Chong, Pradillon, Florence, Lorenzo, Coral Diaz-Recio, Alfaro-Lucas, Joan Manel (2025): Integrative taxonomy of two new peltospirid gastropods from Mid-Atlantic Ridge hot vents, including a potentially symbiotic species. Zoological Journal of the Linnean Society 204 (2), DOI: 10.1093/zoolinnean/zlaf055, URL: https://doi.org/10.1093/zoolinnean/zlaf055
EB228790FF96FFC645C5FA43B1F90ACB.taxon	materials_examined	Type species: Lirapex humatus Warén & Bouchet, 1989, by original designation.	en	Chen, Chong, Pradillon, Florence, Lorenzo, Coral Diaz-Recio, Alfaro-Lucas, Joan Manel (2025): Integrative taxonomy of two new peltospirid gastropods from Mid-Atlantic Ridge hot vents, including a potentially symbiotic species. Zoological Journal of the Linnean Society 204 (2), DOI: 10.1093/zoolinnean/zlaf055, URL: https://doi.org/10.1093/zoolinnean/zlaf055
EB228790FF99FFC64721FB60B1D60A58.taxon	description	(Figs 2 – 6) ZooBank registration LSID: urn: lsid: zoobank. org: act: FB 2 B D 3 E 1 - 1 D 48 - 4217 - 83 A 2 - FAAC 1 BD 39 AC 4 Diagnosis: A very large Peltospira, ≤ 25 mm SD. The shell is globose, rather tightly coiled, with a deep suture. The aperture is very large, expanding rapidly in the adult body whorl. The epipodium carries 24 – 28 thick, short, paddle-like epipodial tentacles along the posterior two-thirds of the foot. The operculum is lacking in adults. The oesophageal gland is greatly hypertrophied. Etymology: From Gargantua, a giant king depicted in the French writer François Rabelais’ novel series The Five Books of the Lives and Deeds of Gargantua and Pantagruel (Les Cinq livres des faits et dits de Gargantua et Pantagruel) (Rabelais 1534). The word Gargantua has since been used to mean ‘ huge’ or ‘ immense’, as exemplified by the English adjective gargantuan. Thus, the species name refers to the very large size of the new species in relationship to other known congeners. Used as a noun in apposition. Type locality: On black smoker chimneys of Hydra hydrothermal vent field (24.96 ° N, 45.57 ° W; ~ 3750 m deep) on the Grappe Deux non-transform offset, MAR (Fig. 2). Type material: Holotype (MNHN-IM- 2000 - 39943), SD 22.5 mm, SH 18.3 mm, 95 % ethanol (Fig. 3 A); on black smoker chimney of Hydra vent field (24.9600 ° N, 45.5749 ° W; 3739 m deep), collected by the manipulator of HOV Nautile with a chimney sample during dive # 2099 (BICOSE 3 dive # 17), R / V Pourquoi pas? cruise BICOSE 3, 16 November 2023. Paratype 1 (SMF 380299), SD 24.6 mm, SH 22.3 mm, 95 % ethanol (Fig. 3 B), same data as the holotype. Paratype 2 (NSMT-Mo 79606), SD 17.6 mm, SH 14.5 mm, 95 % ethanol (Fig. 3 C), same data as the holotype. Paratype 3 (MNHN-IM- 2000 - 39944), SD 19.7 mm, SH 16.9 mm, 95 % ethanol (Fig. 3 D), same data as the holotype. Paratype 4 (SMF 380300), SD 20.1 mm, SH 17.7 mm, 10 % buffered formalin, specimen decalcified for anatomical examinations; on black smoker chimney of Hydra vent field (24.9600 ° N, 45.5748 ° W; 3740 m deep), collected by a suction sampler on HOV Nautile during dive # 2097 (BICOSE 3 dive # 15), R / V Pourquoi pas? cruise BICOSE 3, 14 November 2023. Paratype 5 (SMF 380301), SD 16.9 mm, SH 14.7 mm, buffered formalin, specimen decalcified for anatomical examinations; same data as paratype 4. Other material examined: Lot of three specimens (SMF 380302), 95 % ethanol, on a black smoker chimney of Hydra vent field (24.9598 ° N, 45.5749 ° W; 3799 m deep), sampled using the suction sampler of the ROV SuBastian during dive # 498 on-board R / V Falkor (too), cruise FKt 230303, 28 March 2023. Lot of three specimens (NSMT-Mo 79607), 10 % buffered formalin, on a black smoker chimney of Falkor EMARK vent field (23.4735 ° N, 44.9866 ° W; 3993 m deep), sampled using the suction sampler of the ROV SuBastian during dive # 495 on-board R / V Falkor (too), cruise FKt 230303, 23 March 2023. Lot of three specimens (MNHN-IM- 2000 - 39945), 10 % buffered formalin, on a black smoker chimney of Falkor EMARK vent field (23.4735 ° N, 44.9866 ° W; 3993 m deep), sampled using the suction sampler of the ROV SuBastian during dive # 495 on-board R / V Falkor (too), cruise FKt 230303, 23 March 2023. Seven planktonic larval specimens collected near Hydra vent field by an autonomous plankton pump (SALSA) ~ 30 m from the active edifice, R / V Pourquoi pas? cruise BICOSE 3, used for SEM of protoconch, then DNA barcoding to confirm species identity. Description: The shell (Fig. 3) is very large for the genus (≤ 25 mm diameter), globose, its shape transitioning from skeneiform to haliotiform along growth. Rather tightly coiled, with about two whorls; the suture is deep. The calcareous layer of the teleoconch is thin, pure white, and fragile. The diameter of the shell whorl rapidly expands, especially on the body whorl. The spire is depressed. The shape of the aperture is depressed oval, elliptic, very large, and holostomous. The outer lip is simple and not thickened even in adults, while the inner lip forms a thickened callus on the columella. The shell sculpture consists of regularly spaced but only weakly raised axial ribs, most evident on the first teleoconch whorl; this axial sculpture becomes more irregular on the second teleoconch whorl. In some specimens the axial ribs continue to form throughout the second teleoconch whorl (Fig. 3 B) but in others the ribbing becomes irregular (Fig. 3 A) and in some cases it almost completely vanishes (Fig. 3 C). Near the aperture of adult shells, the axial ribs often become intermittent, forming isolated semi-spherical nodes instead of continuous ribs (Fig. 3 A, B). Specimens from Falkor EMARK tend to have more extensive axial ribbing than those from Hydra. Shell microstructure of the teleoconch (Fig. 4 B) consists of two layers of equal thickness above the myostracum; the inner layer is complex cross-lamellar, and the outer layer is simple prismatic. Both layers exhibit numerous shell pores perpendicular to the shell surface, although the shell pores of each layer appear to have formed independently, and they do not seem to be connected. Protoconch morphology was obtained from pelagic larval stages between 265 and 280 µm in diameter (Fig. 4 A). The protoconch carries 16 – 18 narrow spiral ridges in the first two-thirds (of which seven to eight will be visible apically when the teleoconch develops), and the final one-third is smooth. The peristome of the larval shell is circular when viewed from the bottom and is ~ 150 µm in diameter; the lip is slightly flared. The periostracum is tough, thick, olive green in colour with a strong sheen; its edge is reflected along the shell margin around the entire aperture. The original coloration of the shell surface is usually obscured by dark brown to reddish layers of sulphide mineral deposits. The radula (Fig. 4 C – E) is rhipidoglossate, the formula being ~ 50 + 4 + 1 + 4 + 50 ~. The rachidian tooth is solid, rectangular, and well reinforced by lateral ridges on either side of the shaft. The rachidian cusp is rectangular with a smooth cutting edge that is overhanging, serration lacking. Lateral projections at the base of the rachidian tooth interlock with those from the lateral teeth. The innermost laterals have sigmoidal, interlocking, well-reinforced shafts; the shafts each carry a basal protrusion or node. Lateral cusps are overhanging, blunt triangular in shape, with smooth cutting edges lacking in serrations. The second lateral is similar in morphology to the innermost lateral but slightly taller, with a larger cusp, and its shaft is more straight, with a weaker node. The third lateral is again similar to the second lateral but larger in size, with only a very weak node on the shaft. The outermost lateral is twice as large as the third lateral, with overhanging, sharply pointed triangular cusps bearing two to three denticles only on the outer side of the cutting edge (Fig. 4 D). The marginals are long, with smooth, flattened shafts. The inner marginals (Fig. 4 E) exhibit rake-like cusps serrated into 15 – 20 denticles distally; a major denticle is present near the centre, and the other denticles decrease in strength either side of it. The outer marginals are more elongate, with the cusps becoming increasingly finely serrated but weaker in strength outwards. The animal is gonochoristic, with the external anatomy (Fig. 5 A – D, H, I) lacking in sexual dimorphism or specialized copulatory organs, such as modified cephalic tentacles. The head is large, with a thick and broad snout that expands slightly towards the mouth. The mouth is simple, with oral appendages lacking; a pair of thin, membranous jaws is present. A pair of cephalic tentacles extends slightly beyond the snout in preserved specimens; they are simple and broad at the base, tapering to a blunt tip distally. Sensory papillae are lacking on the cephalic tentacles. There is no trace of eyes visible externally, such as pigmentation. The foot is muscular and fleshy; it is rounded anteriorly but tapered posteriorly. The side of the propodium is covered in irregular tubercles and is demarcated from the epipodium by a narrow fissure. The epipodium carries 24 – 28 thick, short, and paddle-like epipodial tentacles (Fig. 5 B) along the posterior two-thirds of the foot; the tentacles are arranged in a single row. All adult individuals examined lacked an operculum. The mantle edge is simple, with no tentacles. The shell muscle is prominent and U-shaped; the posterior connection is through a narrow attachment and it is laterally expanded anteriorly on both sides, the right side being much larger than the left side (Fig. 5 H, I). The mantle cavity occupies about threequarters of the length. A 3 D reconstruction of the major organs is shown in Figure 6, with calculations of the organ volumes listed in Table 1; the 3 D model is available in an interactive PDF file (Supporting Information, Supplementary Material 1), and a rotating video of the model is also available (Supporting Information, Supplementary Material 2). The circulatory system is dominated by a very large, bipectinate left ctenidium (Figs 5 C, 6 A – E) situated at the left side of the mantle cavity, occupying 15.84 % of the body volume in the specimen measured, terminating at the posterior edge of the mantle cavity. Approximately the posterior two-thirds of ctenidium are attached ventrally to the left body wall, whereas the anterior one-third is free. The osphradium is present underneath the ctenidium, taking the form of a weakly raised, pigmented band along the anteromedian wall of the left shell muscle. The efferent pallial vein runs along the left shell muscle, left of the ctenidium (Fig. 5 I). A large efferent branchial vein runs dorsally along the axis of the ctenidium, while the efferent branchial vein is also sizeable and is contained within the gill axis (Fig. 5 E). A large blood sinus is present beneath the left side of ctenidium, filled by bluish haemocoel. The left kidney (nephridium) is situated immediately posterior of the ctenidium on the left side of the visceral mass (Fig. 6 A – C, E), separated into two lobes that envelop the pericardium ventrally. Externally, the posterior lobe appears larger (Fig. 5 I). The pericardium (Figs 5 F, 6 A – C) is sizeable, containing a monotocardian heart where the auricle is slightly anterior to the ventricle. The auricle occupies 2.28 % of the body volume in the specimen examined (Table 1). The anterior aorta runs towards the head alongside ventral organs, while being embedded in the hypertrophied oesophageal gland; the posterior aorta branches into numerous blood vessels on the posterior mantle roof to feed organs in the visceral mass (Fig. 5 D). The ventricle occupies 2.21 % of the body volume in the specimen examined (Table 1), it is globular and exceptionally thickened by musculature, with muscle bundles running in irregular directions across the lumen (Fig. 5 G). The digestive system posterior to the ventral mouth opening is overall characterized by a hypertrophied oesophageal gland occupying 13.87 % of the body volume (Table 1) in the specimen examined, in conjunction with a reduced size of the alimentary canal for its body size (Fig. 5 E). The radula ribbon is supported by a single pair of prominent cartilages that come into contact anteriorly (Fig. 6 F) with a pair of salivary glands dorsally. The buccal mass leads posteriorly to a simple, narrow oesophagus. The anterior portion of the oesophagus branches into the dorsal aspect of a fused, blind-ended, and hypertrophied oesophageal gland (Fig. 6 D). This oesophageal gland occupies a large portion of the ventral cavity of the animal, filling all available space and completely engulfing the alimentary canal and the anterior aorta, and comprises a network of semi-enclosed tubes within a glandular mass. Beyond the oesophageal gland, the oesophagus runs further posteriorly to reach the stomach, embedded within the digestive gland at the postero-right side of the visceral mass (Figs 5 A, 6 A – D). The stomach is clearly enlarged in comparison to the oesophagus or the intestine and is connected to the digestive gland occupying the posterior-most part of the visceral mass via several tubular openings (Fig. 6 C). The digestive gland is dark in colour and situated posterodorsal to the gonad, occupying 4.52 % of the body volume in the specimen measured. The intestine is very narrow for the size of the animal, emerging from the ventral right side of the stomach and runs anteriorly to perform two loops while embedded in the oesophageal gland, before turning back to reach slightly left of the stomach, penetrating the digestive gland to emerge on the mantle roof dorsal to the stomach as the rectum (Figs 5 A, 6 D). The rectum runs along the mantle roof anteriorly for about one-third of the mantle cavity, then ends in a simple anus, where faeces are expelled. The stomach and the hindgut were filled by a mixture of black, sediment-like matter and fine sulphide mineral particles, whereas the oesophagus was empty. The reproductive system occupies a prominent part of the visceral mass on the right side, visible on the roof of the mantle cavity immediately anterior to the digestive gland and stomach (Figs 5 A, 6 A, B). In both sexes, the gonad is voluminous and located directly adjacent to the right shell muscle, coiling slightly into the spire whorl posteriorly. In males, a prominent, lobulated prostate in the form of complexly folded ducts is present dorsal to the left part of the testis, which opens in a simple gonopore on the right side of the mantle roof. In females, the gonopore also opens in the same location. The ovary occupied 5.60 % of the body volume in the female specimen measured from μ-CT data (Table 1). Distribution: Known only from Hydra and Falkor EMARK vent fields on the MAR between depths of ~ 3700 and 3950 m (Fig. 1). It forms dense colonies directly on sulphide chimneys, and temperatures recorded from Hydra were between 6.28 ° C ± 2.26 ° C (2.83 ° C – 14.28 ° C, 9 min recording with temperature probe of HOV Nautile, ambient temperature 2.5 ° C). It occurs close to Rimicaris exoculata Williams & Rona, 1986 shrimp aggregates, in a very similar habitat. Remarks: Adults of Peltospira gargantua cannot be confused with any other known members of the genus owing to its very large size, averaging at ~ 20 mm SD, with the largest specimens reaching 25 mm; in comparison to P. smaragdina, P. delicata, and P. operculata that reach only 12 mm and P. lamellifera that barely exceeds 2 mm (McLean 1989, Warén and Bouchet 2001). The shell of P. delicata and P. lamellifera cannot be confused with that of P. gargantua because they are not globose but more flattened haliotiform, with disjunct coiling (McLean 1989, Warén and Bouchet 1989). Unlike P. lamellifera and P. operculata (Warén & Bouchet, 2001), P. gargantua lacks an operculum. The shell of P. smaragdina is the most similar to P. gargantua when at a similar size, especially given that the development of axial sculpture is variable in both species, and both species lack an operculum (Warén and Bouchet 2001). The radula morphology and shell microstructure are also similar between these two species (Warén and Bouchet 2001, Kiel 2004). However, they are easily distinguished from external anatomy of the epipodium, where P. smaragdina possesses only ~ 10 small epipodial tentacles (Warén and Bouchet 2001), which is clearly different from P. gargantua, which has 24 – 28 thick, large, paddle-like epipodial tentacles in a single, continuous row. This arrangement of epipodial tentacles also serves to separate P. gargantua from P. operculata and P. delicata, which have multiple rows of densely packed epipodial tentacles (Fretter 1989). Furthermore, the condition of having such a hypertrophied oesophageal gland is not known from any other Peltospira species (Fretter 1989) and is a clear signal for recognizing P. gargantua as a distinct species, although we note that the internal anatomy of P. smaragdina remains poorly known (Warén and Bouchet 2001) and the condition of the oesophageal gland in that species requires further studies. This feature, combined with its large size, means that P. gargantua superficially resembles giant, endosymbiotic peltospirids in genera Gigantopelta and Chrysomallon (Chen et al. 2015 a, c). The arrangement of epipodial tentacles and the radular characters would easily separate them upon closer examination, however. In addition, the lack of both a large operculum (as in Gigantopelta) and dense sclerites on the foot (as in Chrysomallon) also serves to distinguish P. gargantua from those two genera of giant peltospirids. The protoconch of P. gargantua is very similar in overall shape and sculpture to other Atlantic and Pacific Peltospira species (Mullineaux et al. 1996, Warén and Bouchet 2001, Mills et al. 2009), although it appears to be slightly larger.	en	Chen, Chong, Pradillon, Florence, Lorenzo, Coral Diaz-Recio, Alfaro-Lucas, Joan Manel (2025): Integrative taxonomy of two new peltospirid gastropods from Mid-Atlantic Ridge hot vents, including a potentially symbiotic species. Zoological Journal of the Linnean Society 204 (2), DOI: 10.1093/zoolinnean/zlaf055, URL: https://doi.org/10.1093/zoolinnean/zlaf055
EB228790FF99FFC94745FBC9B2D90BBD.taxon	materials_examined	Type species: Peltospira operculata McLean, 1989, by original designation.	en	Chen, Chong, Pradillon, Florence, Lorenzo, Coral Diaz-Recio, Alfaro-Lucas, Joan Manel (2025): Integrative taxonomy of two new peltospirid gastropods from Mid-Atlantic Ridge hot vents, including a potentially symbiotic species. Zoological Journal of the Linnean Society 204 (2), DOI: 10.1093/zoolinnean/zlaf055, URL: https://doi.org/10.1093/zoolinnean/zlaf055
