identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
366E87EDFF89FFD04743FDC3FA678976.text	366E87EDFF89FFD04743FDC3FA678976.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symmetromphalus mithril Chen & Poitrimol & Matabos 2025	<div><p>Symmetromphalus mithril sp. nov.</p><p>(Figs 3–5)</p><p>Symmetromphalus aff. hageni Woodlark – Poitrimol et al. 2022: table 4.</p><p>LSID: urn:lsid:zoobank.org:act: 8A58ADAB-4B10-4563-84E3- 8EE1E83D352E</p><p>Diagnosis: A  Symmetromphalus with silvery white periostracum, protoconch size 220–230 μm, teleoconch lacking broad and raised radial ribs, and radula with 10–12 pairs of marginal teeth.</p><p>Etymology: ‘ Mithril ’, meaning ‘grey glitter’ in Sindarin (Tolkien 1954), a fictional silvery metal. Named in allusion to the silvery colouration and sheen of the periostracum in comparison to other congeners, used as a noun in apposition.</p><p>Type locality: <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=155.05269&amp;materialsCitation.latitude=-9.799067" title="Search Plazi for locations around (long 155.05269/lat -9.799067)">La Scala hydrothermal vent field</a>, Woodlark Basin, 9°47.944 ʹ S, 155°03.161 ʹ E, 3388 m deep, R/V L’Atalante CHUBACARC cruise, ROV Victor 6000 dive 738, 28 May 2019. Taken from Ifemeria nautilei assemblages (Fig. 2A). Type material: Holotype (female), MNHN-IM-2019-30328 (Fig. 3A)  .  Paratype #1 (male), SMF 372653 (Figs 3B, 5A) .  Paratype #2 (female), NSMT-Mo 79457 (Fig. 5B). Paratype #3 (female), MNHN-IM-2019-30329 .  Paratype #4 (female), SMF 372654 (Fig. 3C) .  Paratype #5 (male), NSMT-Mo 79458 (Fig. 3D) .  Paratype #6 (female), MNHN-IM-2019-30330, COI barcode GenBank accession OK635567 .  Paratype #7 (female), SMF 372655, COI barcode GenBank accession OK635568 .  Paratype #8 (male), NSMT-Mo 79459, COI barcode GenBank accession OK635569 .  Paratype #9 (male), SMF 372656, COI barcode GenBank accession OK635570 .  Paratype #10 (female), NSMT-Mo 79460, COI barcode GenBank accession OK635571. All specimens were from the same collecting event at the type locality and preserved in 80% ethanol. Paratypes #6–10 were used for barcoding, with only the head and shell left. For shell measurements of the types, see Table 1.</p><p>Description: Shell (Figs 3A–D, 4A) medium-sized for genus (SL ≤ 12.7 mm), coiled as juveniles but rapidly expanding to become limpet-shaped as adults. Aperture oval, wavy, irregularly shaped, conforming to substrate morphology. Protoconch (Fig. 4B) diameter 220–230 μm, first half with irregular net-like sculpture, gradually fading into completely smooth second half. First whorl of juvenile teleoconch smooth, tightly coiled. At ~ 1 mm shell length, strong spiral (appears radial in adults), nodulous ribs appear; coinciding with rapid expansion of the aperture shifting to limpet-form. Number of ribs initially ~40 but increases to ~ 200 in adults. Apex approximately at mid-line as adults. Interior of shell white, with silky sheen. Shell muscle scar horseshoe-shaped, only weakly marked. Shell microstructure consisting of two layers dorsal to myostracum, with a thin simple prismatic layer outside a thick complex crossed lamellar layer. Periostracum thin, semi-transparent, bluish-white, with a silvery, silky sheen, slightly overhanging at shell edge. Numerous shell pores penetrate both layers of shell but not periostracum (Fig. 4C, D).</p><p>Operculum (Fig. 4E) present, thin, film-like, nearly transparent, vestigial in adults. Early volutions multispiral, final volution rapidly expanding, resulting in distinctly semi-circular shape in adults.</p><p>Radula (Fig. 4F, G) rhipidoglossate, formula 10–12 + 4 + 1 + 4 + 10–12. Rachidian with triangular, well-reinforced base; narrow, triangular, overhanging cusp completely smooth. Three inner laterals interlocked at base, slightly increasing in size from inner to outer; cusps triangular, overhanging, smooth. Outermost lateral much larger, inner cutting edge smooth but outer cutting edge finely serrated, with lowermost serration much stronger than others. Marginals all similar in morphology, with long shafts ending in rounded, comb-like cusps finely serrated all over; lowermost serration on outer edge much larger, denticle-like.</p><p>Soft parts are shown in Figures 3 and 5. Head large, eyes lacking. Gonochoristic, sexually dimorphic. In females, cephalic tentacles short, of equal size but in males left cephalic tentacle greatly enlarged to function as penis, lappet-like when expanded but rolled up as seminal groove, with tubule-like structure present at distal tip. Snout lacking oral disc, with two prominent, ventrally grooved oral lappets. Neck long, laterally compressed; in males, left edge enlarged to form deep seminal groove. Foot circular in outline; anterior pedal gland opening narrow, slit-shaped. Epipodial ridge bearing 8–10 symmetrically distributed epipodial tentacles on posterior two-thirds of foot. Shell muscle horseshoe-shaped, broad anteriorly but narrowing rapidly towards posterior edge, where two arms are connected by a narrow muscular ridge; slightly asymmetrical, with right arm slightly shorter but broader than left. Mantle edge apparently smooth to the naked eye but carries numerous fine papillae. Mantle cavity deep, extending to approximately half the length of the shell muscle. Bipectinate ctenidium (gill) very large, extending beyond pallial edge to reach anterior edge of head. Heart monotocardian; pericardium elongated, with auricle directly anterior to ventricle. Visceral mass small, dorsally occupied by testis or ovary depending on sex, with prostate gland or oviduct directly anterior to gonad on pallial roof. Digestive gland and kidney visible to left of gonad, right of pericardium. Rectum emerges to right side of gill, ending in anus at right side of pallial roof. Rest of digestive system agrees well with condition of genus described previously (Beck 1992).</p><p>Distribution: Known only from the La Scala vent field, Woodlark Basin.</p><p>Remarks:  Symmetromphalus mithril is the fourth species described in its genus, which has been found only in southwestern Pacific hydrothermal vent habitats. The new species can be distinguished from the other three based on a combination of shell and radular characters, as follows (McLean 1990, Beck 1992, Chen and Sigwart 2023). The protoconch diameter of 220–230 μm in  Symmetromphalus mithril is similar to that of  Symmetromphalus regularis (220 μm) but is larger than that of  Symmetromphalus hageni (160–180 μm) and  Symmetromphalus mcleani (180 μm). In  Symmetromphalus mithril, the periostracum is thin and always bluish white with a silvery sheen across the entire size range, as opposed to the thick, tan periostracum in  Symmetromphalus regularis . Although the periostracum is also thin and can range from white to yellowish brown in  Symmetromphalus hageni and  Symmetromphalus mcleani, this generally changes with growth, and in adults they are typically yellowish brown. Nevertheless, periostracum coloration might vary according to the environment, and future findings of  Symmetromphalus mithril from other localities might broaden the range of variability of this character in this species. The shell sculpture of  Symmetromphalus mithril consists of only dense, fine radial ribs, like  Symmetromphalus regularis and  Symmetromphalus hageni, lacking the broad radial ribs seen in  Symmetromphalus mcleani . The radula of  Symmetromphalus mithril is similar to  Symmetromphalus mcleani in that the marginal teeth are reduced to only 10–12 pairs, as opposed to 13–15 pairs in  Symmetromphalus regularis and  Symmetromphalus hageni .</p></div>	https://treatment.plazi.org/id/366E87EDFF89FFD04743FDC3FA678976	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Chen, Chong;Poitrimol, Camille;Matabos, Marjolaine	Chen, Chong, Poitrimol, Camille, Matabos, Marjolaine (2025): Integrative taxonomy of new neomphaloidean gastropods from deep-sea hot vents of the southwestern Pacific. Zoological Journal of the Linnean Society (Statistics in Society) 203 (2): 1-20, DOI: 10.1093/zoolinnean/zlae064, URL: https://doi.org/10.1093/zoolinnean/zlae064
366E87EDFF85FFD44596FE1BFB098990.text	366E87EDFF85FFD44596FE1BFB098990.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symmetriapelta becki Chen & Poitrimol & Matabos 2025	<div><p>Symmetriapelta becki sp. nov.</p><p>(Figs 6–8)</p><p>‘ Mediapex ’ sp. – Zhong et al. 2022: table 1.</p><p>LSID: urn:lsid:zoobank.org:act: D75D67CD-63B8-4FA5- 978E-2A8085075EA6</p><p>Diagnosis: A  Symmetriapelta with all radial ribs being of equal strength and carrying only very fine to no serrations on the three innermost lateral teeth.</p><p>Etymology: Named in honour of the late German malacologist Lothar A. Beck (Philipps-University of Marburg) who studied vent limpets from North Fiji and Lau Basins in the 1990s (Chen and Sigwart 2023). Beck had evidently already noticed the presence of two distinct forms of  Symmetriapelta in North Fiji and Lau Basins, because he separated a vial containing specimens of  Symmetriapelta becki labelled ‘fine’ (i.e. fine sculpture), whereas those containing  Symmetriapelta wareni were marked ‘stark’ (i.e. stronger sculpture). Although at the time Beck apparently did not consider these two forms to be distinctive at the species level, we nevertheless dedicate the specific epithet of  Symmetriapelta becki in recognition of his observations and work.</p><p>Type locality: <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-174.65347&amp;materialsCitation.latitude=-15.4146" title="Search Plazi for locations around (long -174.65347/lat -15.4146)">Mangatolo hydrothermal vent field</a>, northern Lau Basin, 15°24.876 ʹ S, 174°39.208 ʹ W, 2031 m deep, R/V L’Atalante CHUBACARC cruise, ROV Victor 6000 dive 726, 17 April 2019. Taken from  Alviniconcha assemblages (Fig. 2C). Type material: Holotype, MNHN-IM-2019-30332 (Fig. 6A).   Paratype #1, SMF 372657 ( Figs 6B, 8)  .  Paratype #2, NSMT-Mo 79461 .  Paratype #3, MNHN-IM-2019-30333 (Fig.6C) .  Paratype #4, SMF 372658 .  Paratype #5, MNHN-IM-2019-30334 .  Paratype #6, NSMT-Mo 79462 (Fig. 6D), COI barcode GenBank accession OK635421 .  Paratype #7, SMF 372659, COI barcode GenBank accession OK635447 .  Paratype #8, MNHN-IM-2019-30335, COI barcode GenBank accession OK635448. All specimens from the same collecting event at the type locality and preserved in 80% ethanol. Paratypes #6–8 were used for barcoding, with only the head and shell left. For shell measurements of the types, see Table 1.</p><p>Other material examined: <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-177.25012&amp;materialsCitation.latitude=-14.9423" title="Search Plazi for locations around (long -177.25012/lat -14.9423)">Kulo Lasi hydrothermal vent field</a>, Futuna Arc, 14°56.538 ʹ S, 177°15.007 ʹ W, 1414 m deep, R/V L’Atalante CHUBACARC cruise, ROV Victor 6000 dive 729, 24 April 2019. Living on the tubes of siboglinid tubeworms (Fig. 2B)  .  One specimen, MNHN-IM-2019-30336 (Fig. 6F), shell curved .  One specimen, MNHN-IM-2019-30337 (Fig. 6G), intermediate shell form .  One specimen, MNHN-IM-2019-30338, used for barcoding, with only head and shell left, COI barcode GenBank accession OK635460 .  One specimen, MNHN-IM-2019-30339, used for barcoding, with only head and shell left, COI barcode GenBank accession OK635461 .  One specimen, SMF 372660, used for barcoding, with only head and shell left, COI barcode GenBank accession OK635462 .  One specimen, NSMT-Mo 79463, used for barcoding, with only head and shell left, COI barcode GenBank accession OK635462 .  A series of five specimens, MNHN-IM-2019-30340. A series of five specimens, SMF 372661. A series of five specimens, NSMT-Mo 79464. All specimens preserved in 80% ethanol.</p><p><a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-174.01016&amp;materialsCitation.latitude=-15.397833" title="Search Plazi for locations around (long -174.01016/lat -15.397833)">Niuatahi Seamount hydrothermal vent field</a>, Tonga-Tofua Arc (Fig. 6E), 15°23.870 ʹ S, 174°0.610 ʹ W, 1603 m deep, collected by ROV Quest dive #437 during R/V  Sonne cruise SO263 ‘TONGARIFT’, June 2018. Ten specimens preserved in 70% ethanol, SIO-BIC M19504.</p><p><a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=173.91667&amp;materialsCitation.latitude=-16.983334" title="Search Plazi for locations around (long 173.91667/lat -16.983334)">White Lady</a> hydrothermal vent field, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=173.91667&amp;materialsCitation.latitude=-16.983334" title="Search Plazi for locations around (long 173.91667/lat -16.983334)">North</a> Fiji Basin, 16°59 ʹ S, 173°55 ʹ E, 2000 m deep, collected by the human-occupied vehicle (HOV) Nautile dive # PL12 during R / V  Nadir ‘STARMER II’ cruise, 7 July 1989. Two specimens fixed in 10% formalin and transferred to 70% ethanol, MNHN-IM-2014-7987  .</p><p>Description: Shell (Fig. 6) limpet-shaped, with apex slightly left of mid-line in adults (SL ≤ 6.1 mm). Protoconch (Fig. 7A, B) diameter 200–210 μm; sculpture of sparse, irregular, reticulated network of ridges on first half, rapidly fading into completely smooth second half. First half teleoconch whorl of juveniles smooth, lacking any sculpture except fine growth lines, loosely coiling. This rapidly transitions to limpet-shaped adult shell carrying numerous radial ribs by rapid expansion of oval aperture, more or less symmetrical in adults. Side profile and shape of aperture conform to substrate shape, being nearly flat in specimens from Ifemeria shells or chimneys (Fig. 6A–E) but strongly curved in specimens collected from siboglinid worm tubes (Fig. 6F, G). Radial ribs finely nodulous, always of equal strength across entire shell but strength variable across individuals; number of ribs ranges between ~100 and 250 in adults; those with stronger ribs also carry fewer of them. Interior of shell white, with silky sheen. Shell microstructure (Fig. 7D) consists of two layers dorsal to myostracum, with a very thin homogeneous layer on top of a much thicker complex crossed lamellar layer. Numerous shell pores are present in the complex crossed lamellar layer, opening on ventral side wide but rapidly tapering, ending immediately before reaching homogeneous layer. Shell pores therefore do not penetrate outer homogeneous layer. Periostracum variable shades of greenish to yellowish brown, thin, terminates at shell edge rather than overhanging over it.</p><p>Radula (Fig. 7F, G) rhipidoglossate, formula ~25 + 4 + 1 + 4 + ~25. Rachidian solid, well supported with two distinct lateral ridges on shaft, cusp heart-shaped, tapering distally to a sharp point; cutting edge completely smooth. Three inner laterals with sigmoidal, interlocking shafts, cusps sickle-like, triangular; cutting edge varies from smooth to carrying very fine serrations. Shafts of two innermost laterals always carry additional protrusion or node, which is sometimes also present on third lateral; strength of node on third lateral variable even among rows within each radula ribbon. Outermost lateral much broader than others, with straighter shaft lacking protrusion. Cusps of outermost lateral carry very fine serrations on inner edge, whereas outer edge carries much stronger, coarse denticles. Marginals with long shafts. Size of first few innermost marginals moderate, with rake-like cusps carrying ~15 rather strong denticles. Next set of marginals larger, also with rake-like cusps but serrated into 20–25 finer denticles. These gradually decrease in size outwards, with outermost marginals being much narrower and smaller in comparison to innermost marginals. Across all marginals, lowermost denticle strongest on both sides, with lowest denticle on outer cutting edge being the strongest by far. Outer marginals reduced in width, with hook-like cusps serrated into denticles.</p><p>Soft parts are shown in Figure 8. Head lacking eyes; snout with thick musculature around mouth. Cephalic tentacles triangular, thick at base, rapidly tapering to blunt ends in preserved specimens, extending slightly beyond snout. Neck short. Foot elongated oval; opening of anterior food gland moderate in size, slit-like in appearance. Epipodium well developed as continuous ridge, densely lined with ~60 epipodial tentacles (~30 on either side); often larger primary tentacles alternate with smaller secondary tentacles. Mantle edge lacking large papillae but carrying numerous micropapillae. Shell muscle horseshoe-shaped, with muscles of similar size and strength on two sides connected via a narrow muscular ridge at the posterior edge. Mantle cavity of moderate size extending to about half the length of the shell muscle, occupied anterodorsally by moderate-sized bipectinate ctenidium carrying ~30 filaments. Anterior edge of ctenidium emerges on right side of mantle cavity immediately posterior to right cephalic tentacle. Heart monotocardian, with elongated pericardium lying dorsally on pallial roof posterior of ctenidium; auricle positioned anterior to ventricle. Visceral mass rather small, occupied dorsally by digestive gland, ventrally by gonad (animal gonochoristic). Rectum emerges on right side of mantle cavity, running along right pallial margin, ending in anus positioned on right side of mantle cavity on pallial roof. Operculum absent.</p><p>Distribution: Hydrothermal vents in North Fiji and Lau Basins and the Futuna Arc.</p><p>Remarks:  Symmetriapelta becki co-occurs with its congener  Symmetriapelta wareni in North Fiji and Lau Basin vents (Chen and Sigwart 2023), and the two species can be distinguished based on the shell sculpture. Although the strength of radial ribs in  Symmetriapelta wareni is rather variable, the sculpture is always composed of three to five weaker ribs alternating with one much stronger rib (Chen and Sigwart 2023). In  Symmetriapelta becki, however, all radial ribs are of the same strength. The radial ribs in  Symmetriapelta becki are consistent in strength, and they are typically weaker than in  Symmetriapelta wareni; some specimens of  Symmetriapelta wareni can carry broad, scaly ribs, whereas this is never seen in  Symmetriapelta becki . Furthermore, the radula of  Symmetriapelta becki carries many more marginal teeth (~25) than that of  Symmetriapelta wareni (~18). Another interesting difference is seen in the distribution of epipodial tentacles, whereby in  Symmetriapelta wareni the two posterior-most tentacles are positioned somewhat distant from the rest (although this is not clear from all figures in the description, see Discussion below) but this is not evident in  Symmetriapelta becki .</p><p>The protoconch (Fig. 7C) and shell microstructure (Fig. 7E) of  Symmetriapelta wareni were not figured or described in its original description (Chen and Sigwart 2023). We imaged them using newly collected material from Tui Malila vent field, Lau Basin (10 specimens, preserved in 80% ethanol, MNHN-IM-2019-30331, Tui Malila vent field, Lau Basin, 21°59.355 ʹ S, 176°34.098 ʹ W, 1886 m deep, R/V L’Atalante CHUBACARC cruise, ROV Victor 6000 dive 722, 4 April 2019, taken from I. nautilei assemblages) and describe them as follows. The protoconch of  Symmetriapelta wareni is 200 μm in diameter and exhibits sparsely distributed, irregular reticulated sculpture formed by cross-cutting low ridges on the first two-thirds of the protoconch, whereas the last one-third is smooth. This differs from  Symmetriapelta becki, in which only slightly less than half of the protoconch is sculptured (Fig. 7A). The shell microstructure of  Symmetriapelta wareni is virtually identical to that of  Symmetriapelta becki, with a very thin homogeneous layer outside a much thicker complex crossed lamellar layer, and with numerous shell pores penetrating only the complex crossed lamellar layer.</p><p>For morphological distinction from  Symmetriapelta radiata, see Remarks section of that species below.</p></div>	https://treatment.plazi.org/id/366E87EDFF85FFD44596FE1BFB098990	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Chen, Chong;Poitrimol, Camille;Matabos, Marjolaine	Chen, Chong, Poitrimol, Camille, Matabos, Marjolaine (2025): Integrative taxonomy of new neomphaloidean gastropods from deep-sea hot vents of the southwestern Pacific. Zoological Journal of the Linnean Society (Statistics in Society) 203 (2): 1-20, DOI: 10.1093/zoolinnean/zlae064, URL: https://doi.org/10.1093/zoolinnean/zlae064
366E87EDFF81FFD64589FE5FFDF68F7D.text	366E87EDFF81FFD64589FE5FFDF68F7D.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Symmetriapelta radiata Chen & Poitrimol & Matabos 2025	<div><p>Symmetriapelta radiata sp. nov.</p><p>(Figs 9–11)</p><p>LSID: urn:lsid:zoobank.org:act: 187A29B5-FE50-40F1-8288- F5FD68A2C33A</p><p>Diagnosis: A  Symmetriapelta with greenish white periostracum, radial ribs of variable strength on the shell, and carrying strong serrations on the three innermost lateral teeth.</p><p>Etymology:  ‘ Radiata ’, Latin (feminine adjective in the nominative singular), meaning ‘radiated’. Refers to the numerous radial ribs on the shell spreading out from the apex.</p><p>Type locality: <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=155.05269&amp;materialsCitation.latitude=-9.799067" title="Search Plazi for locations around (long 155.05269/lat -9.799067)">La Scala hydrothermal vent field</a>, Woodlark Basin, 9°47.944 ʹ S, 155°03.161 ʹ E, 3388 m deep, R/V L’Atalante CHUBACARC cruise, ROV Victor 6000 dive 738, 28 May 2019. Taken from I. nautilei assemblages (Fig. 2A). Type material: Holotype, MNHN-IM-2019-30341 (Fig. 9A)  .  Paratype #1, SMF 372662 (Figs 9B, 11) .  Paratype #2, NSMT-Mo 79465 (Fig. 9C) .  Paratype #3, MNHN-IM-2019-30342 (Fig. 9D) .  Paratype #4, SMF 372663 .  Paratype #5, NSMT-Mo 79466 .  Paratype #6, MNHN-IM-2019-30343, COI barcode GenBank accession OK635421 .  Paratype #7, SMF 372664, COI barcode GenBank accession OK635439 .  Paratype #8, NSMT-Mo 79467, COI barcode GenBank accession OK635440 .  Paratype #9, MNHN-IM-2019-30344, COI barcode GenBank accession OK635441 .  Paratype #10, SMF 372665, COI barcode GenBank accession OK635442 .  Paratype #11, NSMT-Mo 79468, COI barcode GenBank accession OK635464 .  Paratype #12, MNHN-IM-2019-30345, COI barcode GenBank accession OK635465 .  Paratype lot #13 (growth series of five specimens), MNHN-IM-2019-30346. Paratype lot #14 (growth series of five specimens), SMF 372666, COI barcode GenBank accession OK635465 .  Paratype lot #15 (growth series of five specimens), NSMT-Mo 79469. All specimens from the same collecting event at the type locality and preserved in 80% ethanol. Paratypes #7–12 were used for barcoding, with only the head and shell left. For shell measurements of the types, see Table 1.</p><p>Description: Shell (Fig. 9) limpet-formed, with apex positioned slightly left of mid-line in adults (SL ≤ 6.8 mm). Protoconch (Fig. 10A) diameter 210 μm, sculptured by a sparse, irregular, reticulated network of ridges on first two-thirds, fading into completely smooth final one-third. First 0.5 whorl of juvenile teleoconch smooth, with only fine growth lines, loosely coiling; rapidly developing radial ribs thereafter, together with rapid expansion of aperture to transition into limpet-shaped adult shell. Aperture oval, nearly symmetrical in adults. Radial ribs finely nodulous; strength variable across individuals; in most individuals, all ribs of equal strength (Fig. 9A, C) but some individuals exhibit a pattern where three to seven weaker ribs alternate with one much stronger rib (Fig. 9B, E). Number of ribs between ~100 and 250 in adults; individuals with stronger ribs having fewer of them. Interior of shell white, with silky sheen. Shell microstructure (Fig. 10B) with two clearly discernible layers above myostracum: outer one very thin, homogeneous; inner one much thicker, complex crossed lamellar. Shell pores densely packed in inner complex crossed lamellar layer, not penetrating homogeneous layer. Periostracum variable shades of greenish white, thin, not overhanging shell edge.</p><p>Radula (Fig. 10C, D) rhipidoglossate, formula ~30 + 4 + 1 + 4 + ~30. Rachidian solid, well supported with two distinct lateral ridges on shaft, base rapidly expanding laterally almost at a right angle. Rachidian cusp narrow, heart-shaped, tapering distally to a sharp point; cutting edge smooth. Two inner laterals with sigmoidal, interlocking shafts carrying additional protrusion or node; cusps sickle-like, triangular; inner cutting edge carrying a few strong, coarse denticles; outer cutting edge smooth. Third lateral with similar cusp but shaft straight, without additional protrusion. Outermost lateral much broader than others, with shaft similar to third lateral; cusp carrying strong, coarse denticles on both sides. Marginals with long shafts. Innermost three marginals moderate in size, with rake-like cusps divided into ~15 denticles, transitioning outwards to next set of larger marginals, with more finely serrated cusps divided into ~20–25 denticles. These finely serrated outer marginals decrease in strength outwards, with the last ones being smaller than the innermost marginals.</p><p>Soft parts (Fig. 11) nearly identical to those of  Symmetriapelta becki described above, except for epipodial tentacles being slightly denser, numbering ~70 (~35 on either side). Operculum lacking.</p><p>Distribution: Known only from the La Scala vent field, Woodlark Basin.</p><p>Remarks:  Symmetriapelta radiata is highly variable in the strength of shell radial ribs; although in most individuals the strength is consistent across the entire shell (Fig. 9A, C, D), some alternate between three to five weaker ribs and one much stronger rib (Fig. 9B, E). As such, the shell sculpture cannot be used reliably to distinguish  Symmetriapelta radiata from  Symmetriapelta wareni (Chen and Sigwart 2023) and  Symmetriapelta becki . However, the radula of  Symmetriapelta radiata is clearly distinct from those two species in that the inner side of all four laterals carries a few coarse, strong serrations. In  Symmetriapelta wareni, only the fourth lateral carries very fine serrations on the inner side, whereas the other three laterals have smooth cutting edges (Chen and Sigwart 2023), and in  Symmetriapelta becki all four laterals typically carry very fine serrations, with the three innermost laterals sometimes lacking serration altogether. Furthermore,  Symmetriapelta radiata has denser epipodial tentacles (~35 on either side) compared with  Symmetriapelta becki (~30) and  Symmetriapelta wareni (~26).</p></div>	https://treatment.plazi.org/id/366E87EDFF81FFD64589FE5FFDF68F7D	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Chen, Chong;Poitrimol, Camille;Matabos, Marjolaine	Chen, Chong, Poitrimol, Camille, Matabos, Marjolaine (2025): Integrative taxonomy of new neomphaloidean gastropods from deep-sea hot vents of the southwestern Pacific. Zoological Journal of the Linnean Society (Statistics in Society) 203 (2): 1-20, DOI: 10.1093/zoolinnean/zlae064, URL: https://doi.org/10.1093/zoolinnean/zlae064
