Siphonaria sipho Sowerby I, 1823

Jenkins, Bruce & Köhler, Frank, 2024, Hidden in plain sight: Systematic review of Indo-West Pacific Siphonariidae uncovers extensive cryptic diversity based on comparative morphology and mitochondrial phylogenetics (Mollusca, Gastropoda), Megataxa 13 (1), pp. 1-217 : 22-28

Siphonaria sipho Sowerby I, 1823

( Figs 8–10 , 12A–F, L–M )

Patella sipho Sowerby I 1823 (in 1821–34): [126] (nomen nudum).

Siphonaria sipho Sowerby I 1823 (in 1821–34): [126], pl. 143, fig. 1 (type locality unknown).—Sowerby I 1825: 32; Blainville 1827: 294; Deshayes 1832: 954; Lamarck 1836: 557; Anton 1838: 26; Lamarck 1839: 205; Catlow & Reeve 1845: 100; Gray 1847 a: 181; Sowerby I 1852: 277, 323, fig. 231*; Menke 1844: 55; Gray 1850: 181; Sherborn 1922: 5992; H. Adams & A. Adams 1855 (in 1853–58): 271, pl. 84, fig. 10b; Reeve 1856: pl. 2, species 9; Hanley 1858b: 152; H. Adams & A. Adams 1863: 271; Schrenck 1867: 306; Dall 1870: 31; Fischer 1883 (in 1880–1887): 513, pl. 11, fig. 25); Paetel 1883: 178; 1889: 429; Stearns 1891: 13; Boettger 1892: 168; Tillier & Bavay 1905: 176; Thiele 1931: 472; Abe 1940: 59; Hirase 1941: 94, pl. 121, fig. 11; Kuroda 1941: 137; Kuroda & Habe 1952: 86; Azuma 1960: 62; Berry 1977: 197–198, fig. 15 RS; Galindo 1977: 416; Jenkins 1983: 28; Poppe 2010: 442, pl. 912, figs 1–2; White & Dayrat 2012: 58.

Siphonaria exigua Sowerby I 1823 (in 1821–34): [126], pl. 143, fig. 4 (type locality unknown).—Sowerby I 1820 –1825: 126 [1823], pl. 122, fig. 4, 32 [1825]; Blainville 1827: 295; Lamarck 1836: 557; Anton 1838: 26; Lamarck 1839: 205; Catlow & Reeve 1845: 100; H. Adams & A. Adams 1855 (in 1853–58): 271; Hanley 1858a: 25; 1858b: 151; 1863: 271; H. Adams & A. Adams 1863: 271; Schrenck 1867: 306; Paetel 1873: 117; 1875: 92; 1883: 178; 1889: 428; Schepman 1913: 460; Faustino 1928: 352; Morrison 1972: 52; Berry 1977: 190; Galindo 1977: 416; Trew 1983: 5; White & Dayrat 2012: 63.

Siphonaria radiata Gray 1824: 276 (invalid; unnecessary replacement name; refer to Taxonomic remarks).— Gray 1826: 491; 1827: pl. 4 (6), figs 20–21; White & Dayrat 2012: 67.

Siphonaria cornuta Gould 1846: 11 (type locality: Mangsi [Mangsee Islands, Philippines]).— Gould 1848: 153; 1852: 357; H. Adams & A. Adams 1855 (in 1853–58): 271; Gould 1856: 13, figs 467, 467a, b; Hanley 1858b: 151; H. Adams & A. Adams 1863: 271; Paetel 1889: 428; Faustino 1928: 352; Johnson 1964: 60; White & Dayrat 2012: 62.

Siphonaria siquijorensis Reeve 1856 : species 27, pl. 6, fig. 27a, b (type locality: Island of Siquijor, Philippines).— Hanley 1858b: 152; Paetel 1873: 117; 1883: 178; 1889: 420; Galindo 1977: 416; Trew 1983: 7; Higo et al. 2001: 142, fig. G4974; Poppe 2010: 444, pl. 913, figs 1, 2; White & Dayrat 2012: 67.

Siphonaria luzonica Reeve 1856 : species 29, pl. 6, fig. 29 (type locality: Puteao, Luzon, Philippines).— Hanley 1858b: 152; Paetel 1889: 429; Faustino 1928: 352; Galindo 1977: 416; Trew 1983: 6; White & Dayrat 2012: 65.

Siphonaria corrugata Reeve 1856 : species 31, pl. 6, fig. 31 (type locality: Puteao, Luzon, Philippines).— Hanley 1858b: 151; Paetel 1883: 178; 1889: 428; Faustino 1928: 352; Galindo 1977: 416; Trew 1983: 5; Poppe 2010: 440, pl. 911, figs 1a, b, 2a–c, 3a–c; White & Dayrat 2012: 62.

Siphonaria crebricostata — Schrenck 1867: 306 (not S. crebricostata Jay, 1839 ).

Siphonaria albicans Schrenck 1867: 306 (invalid; incorrect subsequent spelling of albicante Quoy & Gaimard, 1833 ; not S. albicante Quoy & Gaimard, 1833 ).

Siphonaria zelandica — Schrenck 1867: 306 (not S. zelandica Quoy & Gaimard, 1833 ).

Siphonaria punctata — Schrenck 1867: 306 (not S. punctata Quoy & Gaimard, 1833 ).

Siphonaria plicata — Schrenck 1867: 306 (not S. plicata Quoy & Gaimard, 1833 ).

Siphonaria sipho elatior Schrenck 1867: 306 (type locality: Philippinen [ Philippines]). White & Dayrat 2012: 59, 63, 70.

Siphonaria sipho intermedia Schrenck 1867: 307 (type locality: Philippinen [ Philippines]). White & Dayrat 2012: 59, 64, 70.

Siphonaria sipho depressior Schrenck 1867: 307 (type locality: Bai von Hakodate auf Jesso [Hakodate Bay, Hokkaido, Japan]). White & Dayrat 2012: 62, 70.

Siphonaria (Mestasiphon) atra — Habe & Kosuge 1966: 113, pl. 42, fig. 26 (incorrect subsequent spelling of Mestosiphon ) (not S. atra Quoy & Gaimard, 1833 ).

Siphonaria sipho var. sipho — Hubendick 1945: 29.

Siphonaria sipho var. exigua — Hubendick 1945: 29.

Siphonaria (Siphonaria) laciniosa — Hubendick 1946: 47 (not S. laciniosa ( Linnaeus, 1758)) .

Siphonaria (Siphonaria) laciniosa var. exigua — Hubendick 1946: 47 (in part), pl. 3, fig. 16.

Siphonaria (Siphonaria) laciniosa var. sipho — Hubendick 1946: 47 (in part), pl. 3, fig. 17.

Siphonaria laciniosa elatior — Hubendick 1946: 48.

Siphonaria laciniosa intermedia — Hubendick 1946: 48.

Siphonaria laciniosa depressior — Hubendick 1946: 48.

Siphonaria kurracheensis var. siquijorensis — Hubendick 1946: 54.

Siphonaria laciniosa — Kuroda 1960: 43; Okutani 1982: 32; Fukuda 1994: 50, 805 (not S. laciniosa (Linneaus, 1758)) .

Siphonaria javanica forma sipho — Springsteen & Leobrera 1986: 286, pl. 81, figs 21–22.

Siphonaria (Perellsiphon) siquijorensis — Fukuda 1994: 50, 809 (incorrect subsequent spelling of Parellsiphon ).

Siphonaria kurracheensis — Hylleberg & Kilburn 2003: 113 (not S. kurracheensis Reeve, 1856 ).

Siphonaria guamensis — Tan & Kastoro 2004: 50 (not S. guamensis Quoy & Gaimard, 1833 ).

S. laciniosa group ‘unit 24’ (in part)— Dayrat et al. 2014: 261, 266, fig. 4F–I.

Material examined. Type material. Neotype of Siphonaria sipho Sowerby I, 1823 , present designation, from Calalinan , Siquijor, Philippines, 9°12.834’N, 123°30.043’E; coll. B.W. Jenkins, 3 April 2019, PHS02-5 ( NHMUK 20210025 [M412, SK095], Fig. 8A ).

Holotype of Siphonaria cornuta Gould, 1846 from ‘Mangsi’ [= Mangsee] Islands ( USNM 5850 , Fig. 12E ).

Four syntypes of S. siquijorensis Reeve, 1856 from Siquijor ( NHMUK 1969166 , Figs 8K–M ) .

Three syntypes of Siphonaria luzonica Reeve, 1856 from Puteao , Luzon, Philippines ( NHMUK 1979163 , Figs 8B–D ) .

Syntype of Siphonaria corrugata Reeve, 1856 from Luzon , Philippines ( NHMUK 1979165 , Fig. 8E ) .

Other, non-type material. Philippines, Siquijor: Sawang , 09°08.249’N, 123°31.113’E, PHS02-3 ( AM C.585532 20+p, C.585108 p [M404, SK078], C.585109 p [M406, SK074], C.585110 p [M415, SK098], C.585111 p [M477, SK284], C.585112 p [M479, SK286], C.585116 p [SK277], C.585117 p [SK278]); Calalinan, 09°12.834’N, 123°30.043’E, PHS02-5 ( AM C.585908 20+p)); Lazy , 09°07.544’N, 123°38.407’E, PHS03-1 ( AM C.595952 1p) . Cebu: Mactan Point, 10°20.014’N, 124°02.723’E, PHS04-2 ( AM C.585946, 20+p, C.585119 p [M413, SK096], C.585120 p [SK094], AM C.585946 10p) . Bohol: Caubian Is, 10°17.117’N, 124°10.306’E, PHS04- 3 ( AM C.595936 p [SK561]) . Luzon: San Agapito, E side Isla Verde , 13°31.782’N, 121°05.499’E, PHV02-1 ( AM C.585862 p [M407, SK076]), NW Polillo Is, Bolunga District, nr Panukalan , E Quezon , 14°59’N, 121°49’E ( WAM S72342 , 10+p) . Japan, Okinawa: Sun Marina Beach , Onna , 26°27.842’N, 127°48.755’E, JP01-1 ( AM C.585618 9 p); Cape Maeda , 26°26.573’N, 127°46.113’E, JP01-2 ( AM C.585619 9p, C.595925 p [M597, SK541], C.595927 p [M598, SK542], C.595928 p [M599, SK543]); Onna , 26°26.113’N, 127°46.085’E, JP01-3 ( AM C.585620 , 2 p); Moon Bay , Onna, 26°26.653’N, 127°48.230’E, JP01-4 ( AM C.585625 4p, C.584909 p [M506, SK327], C.584910 p [M508, SK323]); Tancha Bay , rocky point, 26°27.941’N, 127°49.194’E, JP01-6 ( AM C.584922 p [M494, SK313], C.584923 p [M497, SK316], C.584924 p [M503, SK324], C.584925 p [M507, SK322]) . Honshu: Boso Peninsula , Tateyama , Arai Bch , seawall, 34°59.838’N, 139°51.378’E, JP01-2 ( AM C.584934 1p [M488, SK307], Fig. 12A, L ) . Indonesia: Riau Islands, NE coast of Pulau Panjang , 04°15.9’N, 108°12.27’E ( ZRC. MOL.24910 [M520], Fig. 8P ), 24911 p [M521], Fig. 8Q ), 24907 p [M517, SK433], 24908 p [M518, SK434]); Anambas, SW Pulau Mubur, Teluk Air Bandung , eastern shore of Pulau Kecik , ZRC EA-ZJ07 ( ZRC. MOL.24909 p [M522]) .

Taxonomic remarks. Siphonaria sipho is the type speciesof Siphonaria bysubsequentdesignation.Thename has widely been used through the taxonomic literature, but it has been treated inconsistently in the past resulting in a confused taxonomic history. Sowerby (1823) referred to ‘ Patella sipho ’ as a ‘common name’, which, to our knowledge, was not described previously and therefore is considered as a nomen nudum. The original type material of S. sipho is considered lost; we found no references to types in previous systematic literature and no type material was located at the NHMUK after an exhaustive search (K. Way & J. Ablett, pers. com.; Art. 75.3.4 of the Code). The neotype of S. sipho ( Fig 8A ), is herein designated to clarify the taxonomic status of this taxon and its type locality in accordance with Art. 75.3 of the Code. This neotype designation aims to remove prevailing uncertainty about the identity of this species and to clarify the taxonomic status of Siphonaria . By designating the neotype, we restrict the type locality of S. sipho to Calalinan, Siquijor, Philippines. Altogether four hand-drawn figures of S. sipho were published in earlier treatments. The original description of this species was published in 1823 while the original black and white drawings were published in 1824 (Sowerby I 1824: pl. 122, fig. 1; Fig. 8O ). Subsequently, the species was depicted by H. Adams & A. Adams (1856: pl. 84, fig. 10b) and Reeve (1856: pl. 2, figs 9a–d) based on specimens from the Philippines. While these figures differ in some respects, they provide a limited number of shell characteristics that aid the identification of this species. Although Sowerby’s (1823) figures of S. sipho are generalized, the proportions, evenness and nature of shell ribbing, and shape/shading of the interior shown in these figures, closely match the characteristics of topotypic specimens of S. luzonica Reeve, 1856 rather than any other Indo West-Pacific species. Based on this close similarity in shell features, we treat S. luzonic a as a junior synonym of S. sipho . Figures of S. sipho in Reeve (1856: pl. 2, fig. 9a–b, [specimen 1] from Philippines) and H. Adams & A. Adams (1856: pl. 84, fig. 10b; no location) closely match Sowerby’s figure of S. sipho . Reeve’s second figure of S. sipho (1856: pl. 2, fig. 9c–d [specimen 2] from Philippines), however, differs from the first specimen. It is closely similar with Reeve’s (1856: pl. 6, fig. 29a–b) coloured figures of S. luzonica and with Reeve’s (1856: pl. 6, fig. 31a–b) coloured figures of S. corrugata .

Our delineation of S. sipho is based on comparative analyses of the morpho-anatomy and mitochondrial genetics of the neotype and freshly collected topotypes of S. sipho depressior ( Figs 8 I ) and a geographic series of additional specimens (Tables S1–2), including topotypes of S. exigua ( Figs 8J ), and specimens closely matching the types of S. luzonica and S. corrugata , respectively ( Figs 8B–D, E ).

Sowerby I (1823) described Siphonaria exigua by reference to the unavailable name Lepas exigua published in Martini & Chemnitz (1769: 92, figs 88–89) (work on the Official Index of rejected and invalid works in zoological nomenclature). The original figure of “ Lepas exigua ” is similar to the shell depicted in Sowerby I (1823: pl. 143, fig.4) by absence of a prominent siphonal ridge and the configuration of ribs. Therefore, we treat S. exigua Sowerby I, 1823 as a junior synonym of S. sipho .

Gray (1824: 276) introduced S. radiata as a substitute name for all species figured by Sowerby’s (1823) (i.e. S. sipho , S. concinna , S. exigua and S. tristensis ) instead of using one of these names stating that “he [Sowerby] has … fallen into the common error of modern conchologists, of making too many species; for I have good reason to believe that all the specimens that he has figured, except S. tristensis , …. belong to one species”. Siphonaria radiata Gray (1824: 276) therefore is an unnecessary replacement name and permanently invalid. Gray (1847 a: 181) subsequently reverted to using the name S. sipho as the type species of the genus. Siphonaria cornuta Gould, 1846 was described for shells collected at Mangsee Islands, Sulu Sea during the ‘ United States Exploring Expedition’. The shells were figured subsequently by Gould (1856). Gould (1846 b: 11) indicated that S. cornuta was allied to S. atra . Johnson (1964: 60) listed Gould’s (1856) figured specimen as the ‘holotype’ and mentioned additional paratypes (3 paratypes MCZ 88100 ex BSNH 3763, original no. 792; 3 paratypes MCZ 216757 ex Smithsonian Inst.). As the original description does not contain an original type designation, Johnson’s (1964: 60) subsequent reference to the holotype qualifies as a lectotype designation (Art. 74.6 of the Code). The shell sculpture and geometry of the holotype of S. cornuta (i.e., elongate shell, low profile primary ribs, strong protruding shell edge ribbing, interior shell edge colouration and interstice secondary ribbing, Fig. 12E ) closely matches diagnostic features of S. sipho . For this reason, we treat S. cornuta as a junior synonym of S. sipho . Pilsbry (1895: 5) considered S. cornuta as a synonym of S. atra . However, the holotype of S. cornuta differs from the more circular geometry and less protruding edge ribbing of S. atra . Therefore, we reject Pilsbry’s synonymization.

Siphonaria siquijorensis Reeve, 1856 was described from the Island of Siquijor, Philippines. One syntype is figured in Higo, Callomon & Gotō (2001: 142, fig. G4974, “BMNH 1969166”). While topotypic specimens matching the shell form of syntypes were not found in this study, the shell morphology of specimens of S. sipho from Okinawa, Japan ( Fig. 12B–C ) match the shell sculpture and geometry of syntypes of S. siquijorensis ( Figs 8K– M ). For this reason, we treat S. siquijorensis as a junior synonym of S. sipho . The record of S. siquijorensis in Hedley (1909: 369, Qld) is outside of the known distribution of S. sipho ; likely a misidentification of either S. atra or S. opposita .

Schrenck (1867: 306) described three infraspecific taxa (elatior, depressior and intermedia), all intended to describe the extent of intraspecific variation within this species, stating ‘former and the latter of these forms are available to us from the Philippines, the second, ... from the fauna area in question, the North Japan Sea’. The subspecies depressior was recorded from ‘Bai von Hakodate auf Jesso’ [Hakodate Bay, Hokkaido, Japan]. Hubendick (1946: 48) treated all three taxa as junior synonyms of S. sipho . Mitochondrial and comparative anatomical data presented here reveal that specimens matching these nominal taxa are well contained within the range of intraspecific morphological variation of S. sipho . Therefore, we maintain their treatment as synonyms of S. sipho .

Reeve (1856) incorrectly listed several species as synonyms of S. sipho (i.e., S. crebricostata [nomen nudum; refer below], S. albicans [ sic albicante = S. atra ], S. zelandica [ Australia], S. punctata [ Mauritius], and S. plicata [ Tonga]). Schrenck (1867: 306) and Hutton (1880: 36, adding S. inculta Gould ) appear to have accepted Reeve’s synonymy. The listing of S. exigua in Adcock (1893: 11) as synonym of S. luzonica (from SA; misidentified S. zelandica ) is erroneous. The identity of ‘ S. sipho Sow. ’ in Vernhout (1913: 252, from Ceram) is implausible for being well outside the known distribution of S. sipho . It possibly refers to S. costellata sp. nov. described herein.

The identity of S. sipho in Hutton (1880: 36, 1883: 143, from New Zealand) is unclear and most likely a misidentification of S. australis ( Jenkins, 1983: 11) . The synonymy given by Hutton (1880) is incorrect and includes distinct species. Therefore, the stated distribution of S. sipho (‘ Philippine Islands, Indian Archipelago, Mauritius, Tonga, Chatham Islands, Auckland to Dunedin [ NZ]’) is also incorrect.

Hubendick (1946: 47) treated S. sipho and S. exigua as intraspecific taxa within S. laciniosa , most likely based on the type specimen of Patella laciniosa Linneaus, 1758: 781 , held at UUZM. Examination of type specimens and morpho-anatomy in this study reveal that Hubendick’s interpretation of S. sipho is based on misidentifications of S. javanica , S. viridis and S. sipho . His synonymization of S. sipho with S. laciniosa is rejected. Kuroda (1960: 43) also incorrectly synonymized S. sipho Sowerby with S. laciniosa . He listed ‘ S. laciniosa ’ from Okinawa (unfigured). We consider this record to be identical either with S. sipho or S. tanchaensis sp. nov., both found in Okinawa and exhibiting shells very similar to S. laciniosa . Morrison (1972) treated S. sipho as a junior synonym of S. laciniosa ‘ Lamarck, 1819 ’ along with 26 other nominal species based on similarity to a ‘ laciniosa ’ shells figured throughout the literature and a ‘common reproductive development’. These synonymies are not supported by examination of type specimens and comparative morpho-anatomy and are therefore rejected.

External morphology ( Figs 8T–U , 12L–M ). Foot sole dark grey, foot edge pale yellow, unpigmented; foot wall, pneumostome and cephalic lobes pale greyish yellow, covered in irregular blotches of black pigmentation; mantle thin, translucent, pale yellowish grey, edge thickened, lobed, with black pigmentation edge bands aligning with underside of rib interstices.

Shell ( Figs 8 , 12A–F ; Table S9). Highly variable, medium sized (max sl mean = 16.8 mm, SD = 2.9 mm, n = 9), circular ovate, low to commonly tall; thick, apex offset central sightly to posterior and left, apical sides straight to convex, sometimes strongly convex ( Figs 8G–H, J ); protoconch homostrophic (n = 2; Figs 8V ), shell whorl dextral; shell exterior and edge usually uneven; growth striae prominent in bands; rib count (mean = 37, SD = 5; n = 9), 10–12 fairly evenly spread primary ribs, pale white, raised rounded ridges, widen to shell edge, protrude beyond shell lip to unevenly scallop and corrugate the edge, ends of primary ribs may be flared creating uneven roughness on rib ridges, between primary ribs brown flecks/bands with two to six finer whitish secondary ribs (sometimes none), rib interstices narrow, darker; paired primary ribs on siphonal ridge, no more prominent than other primary ribs. Interior shell margin white to cream, dark brown markings on shell edge align under rib interstices may extend over shell margin (as in Sowerby’s original figure), white rays align on shell margin under primary/secondary ribs, ADM distinct, varies from tan to dark brown; siphonal groove distinct, same colour as shell edge; spatula golden tan with central white to dark chocolate brown; ADM scar distinct, brown to white as spatula; cephalic muscle weakly convex; thickening and whitening of shell lip common, translucent, infills and reduces lip scalloping, spatula becomes whitened.

Neotype ( Fig. 8A ). Shell (sl = 18.7, sw = 14.4, sh = 6.3 mm) circular ovate, medium; thick, apex offset weakly to posterior and left, ~14 primary ribs, with 1–3 in between finer secondary ribs; siphonal ridge formed by adjacent dual primary ribs. Interior shell lip and margin white under ribs, dark brown rays on shell lip aligning under rib interstices; taller and slightly darker interior shell form of S. sipho . RS ( Fig. 9A ).

Reproductive system ( Figs 9–10 ; n = 15). Positioned to the right side of coelom, against foot wall, on foot muscle and under the respiratory cavity; epiphallic parts positioned over BM and between RAM; GA very small, with singular GP through foot wall; AO large, base wide, elongated, tip bluntly pointed and solidly embedded in MG, joined to lower ED and upper GA; ED as long as AO, narrow, centrally bent, joins to outer side of GA; GA, AO, ED all white muscular fibrous tissue; EG soft whitish tissue, slightly folded, medium in size, joins end of ED; single flagellum (F1), short, often looped, appears as an extension of broader ED; BD and CD connect closely but in opposing directions into GA between ED join and GP, BD narrower and longer, both smooth, whitish, featureless, pass closely together through outer side of RAM ( BD over CD) into soft white folded tissues of MG; MG / AG complex may be large; CD connecting to ducts; BD with large distal loop often looping behind ED, MA often present; BC small, embedded in top of AG, spherical, thin whitish translucent test; HD short, small, folded, links ducts in soft white folded tissues of AG to yellowish granulated HG; AG similar size to HG, sides match curvature of inner foot wall.

Spermatophore ( Figs 9C, G , 10B ). Thread-like (mean total length = 3.63mm, SD = 1.06mm, n = 2), translucent, test thin; head section, tip bluntly rounded, evenly cylindrical, elongate, containing a white gelatinous mass; taper region into the filamentous transparent flagellum is short; both sections smooth, featureless. Head shorter and thicker than flagellum (mean head length = 1.46 mm, SD = 0.11 mm, n = 2; mean of SPM length ~ 41%, SD = 9%; mean head width = 120 μm, SD = 20 μm, n = 2; mean flagellum width = 13 μm, n = 2, SD = 15 μm). Seven SPM tightly coiled in one bursa found in [SK078].

Radula and jaw. Dentition formula 40:1:40 ( Hubendick 1946: 47, misidentified as S. laciniosa ).

Comparative remarks. Siphonaria sipho ( laciniosa group, unit 24) is genetically well-differentiated from other species by COI distances of ≥ 14.9% (Table S6). The sister species of S. sipho is S. rodrigoensis sp. nov. ( Fig. 3 ). The nominal taxa S. luzonica , S. exigua , and S. corrugata are synonymized herein based on examination of topotypic samples. Siphonaria siquijorensis , S. exigua , and S. corrugata are treated as conspecific based on examination of specimens corresponding closely to the types. Shells matching Sowerby’s original figure ( Fig. 8O ), Reeve’s figures of S. sipho and specimens matching Sowerby’s original figure of S. exigua are all conspecific.

Anatomically the RS and SPM of all forms reveal some variation in RS structure (i.e., AO may be very wide and blunt ( Fig. 9D ); and F1 short and (un)looped ( Figs 9B, D–F ). This variation is considered as infraspecific. Siphonaria sipho exhibits a wide range of shell variation, particularly in shell thickness and height, primary and secondary ribbing as well as internal and exterior colouration. This variation appears uncorrelated with shell size or geographical distribution. Shell variability ranges from a heavily ribbed, tall shape (resembling S. exigua ; Fig. 8J ) to a low, finer ribbed shape with ribs aligning closely to the shell edge (i.e., not strongly protruding; resembling S. cornuta , S. luzonica and S. corrugata shell forms). Populations on Riau Island, Indonesia, represent a geographical outlier that is morphologically somewhat distinct but genetically not well-differentiated from other representatives of this species. The Riau Island specimens differ by having a smaller, lower shell, less raised ribbing, weaker edge scalloping, a smaller AO, shorter, narrower ED, and shorter F1.

Throughout the range of S. sipho we found seven congeners occurring in partial sympatry. Four of these are sympatric in the Philippines: The shell of S. bifurcata resembles finer ribbed forms of S.sipho but is distinguished by narrower primary ribs, fewer intervening secondary ribs, a weakly flared siphonal ridge edge, and paler interior colouration as well as by having a smaller AO, GA and a shorter ED. Siphonaria sirius has a lower shell height, a siphonal ridge formed by single rib, a darker exterior and interior, broader and white primary ribs as well as a smaller AO and bursal loop. Siphonaria caubianensis sp. nov. has a lower height, darker exterior and interior, strongly and unevenly scalloped edge, broader and white primary ribs, a larger AO, bursal loop, and smaller BC. Siphonaria alba has broader primary ribs, a shorter, wider ED, and a smaller AO. Four species occur in sympatry with S. sipho in Okinawa: Siphonaria camura sp. nov. and S. rucuana are smaller in shell size, the former having a fragile, evenly brown shell; the latter a combination of less raised shell, even ribbing, and darker interior colouration. Both have a smaller AO, shorter wider unlooped BD, and S. camura sp. nov. has a barbed SPM. Siphonaria subatra has a darker exterior and interior colouration, narrower ribbing, lower shell, a smaller BC, a slightly smaller AO. Siphonaria tanchaensis sp. nov. closely resembles S. sipho anatomically and morphologically; it has a similar shell geometry, colouration and ribbing, and internal colouration (i.e., spatula, shell lip including a thickened white lip form). However, has a taller shell, narrower ribs, and a paler, less banded inner shell lip, a smaller BC, ED and AO, and a shorter SPM. Siphonaria sipho co-occurs with S. japonica in Honshu, and has a lower, thinner, and more fragile shell, dark brown exterior and interior colouration, narrower ribbing, a smaller AO, larger BC, and a barbed SPM. Siphonaria radians , sympatric on Riau Islands, has a lower shell with a more posteriorly offset apex and a multi-ribbed siphonal ridge without a flared edge, a larger AO, longer wider twisted ED and a smaller BC.

Specimens identified as S. sipho from Java, Bali, and PNG by Adam & Leloup (1939) are here attributed to S. viridis . The figure of S. sipho in Hirase (1941: 94, pl. 121, fig. 11) is probably a specimen of S. tanchaensis sp. nov. The RS figured in Hubendick (1945: 31, fig. 48) matches the RS of S. sipho . The RS figure in Hubendick (1945: 31, fig. 52) attributed to ‘ S. kurracheensis ’ differs from RS of S. kurracheensis and is probably of S. sipho .

Specimens from Palawan figured as ‘ Siphonaria javanica ’ in Springsteen & Leobrera (1986: pl. 81, figs 21– 22) are specimens of S. sipho . The record of ‘ S. sipho var. exigua ’ in Subba Rao & Dey (2000: 190) from Andaman and Nicobar Islands is based on a misidentification.

Figured specimens of ‘ S. sirius ’ in Poppe (2010: pl. 913, figs 3–4) are here attributed to S. sipho . Instead, S. sirius typically possesses a single rib forming the siphonal ridge. Specimens figured as ‘unit 25, laciniosa group’ in Dayrat e t al. (2014: fig. 4F, H, I) from Okinawa, Taiwan, and the Philippines are all consistent with characters typical of S. sipho .

Distribution and habitat. Philippines (Bohol, Balicasag, Bandian, Negros, Olango, Siquijor, Mactan, Isla Verde, Cebu, Mangsee Is), Taiwan, Japan (Okinawa, Boso Peninsula, Honshu), Indonesia (Riau and Anambas Islands) ( Fig. 11 ). Commonly found in sheltered locations, such as hollows and crevices, across upper and mid littoral levels, on bare, exposed rocks. Home scars prominent.

Figures

FIGURE 3. Maximum Likelihood phylogram (partial, species not collapsed). Clades J–L (laciniosa and plicata groups) of the tree shown in Fig. 1. Branch labels give specimen identifiers for new sequences or Genbank accession numbers for imported sequences from other studies and geographic regions (see Tables S1–S2 for details). Identical haplotypes are merged into single tips. Numbers on branches indicate branch support by employing 10,000 ultrafast bootstraps. Clade names give unit numbers and accepted species names. Scale bar indicating modelled sequence divergence.

FIGURE 8. Shell morphology of Siphonaria sipho. A. Neotype of S. sipho NHMUK 20210025, Siquijor [M412, SK095]. B–D. Syntypes of S. luzonica NHMUK 1979163, E. Syntype of S. corrugata NHMUK 1979165. F. TS of S. siquijorensis, Siquijor, AM C.585108 [M404, SK078]. G. Polillo Is, WAM S113803 [SK101]. H. Siquijor, AM C.585110 [M415, SK098]. I. Okinawa, Tancha Bay,AM C.584923 [M497, SK316]. J. S. exigua morph, Siquijor,AM C.585111 [M477, SK284].K–M. Syntypes of S. siquijorensis NHMUK 1979166. N. Cebu, AM C.585119 [M413, SK096]. O. Sowerby’s original figure of S. sipho. P. Indonesia, Riau Islands, ZRC.MOL.24910 [M520]. Q. Riau Islands, ZRC MOL.24911 [M521, SK437]. R. Philippines, Isla Verde, AM C.585862 [M407]. S. Cebu, AM C.585120 [SK094]. T–U. Animal in situ, Siquijor, PHS02-5. V. Protoconch, Siquijor, AM C.585116 [SK277]. Unlabelled scale bars = 10 mm.

FIGURE 9. Reproductive morphology of Siphonaria sipho. A. Neotype of S. sipho NHMUK 20210025 [M412, SK095], Siquijor. B–C. TS of S. luzonica and S. siquijorensis, Siquijor, AM C.585108 [M404, SK078]. D. TS of S. corrugata, Polillo Is, WAM S113803 [SK101]. E. Okinawa, Tancha Bay, AM C.584923 [M497]. F–G. S. exigua morph, Siquijor, AM C.585111 [M477, SK284]. Scale bars = 1 mm.

FIGURE 10. Reproductive morphology of Siphonaria sipho, continued. A. RS, Indonesia, Riau Is, ZRC.MOL.24910 [M520, SK436]. B. SPM (same individual). Scale bars = 1 mm.

FIGURE 11. Occurrence records of S. sipho, S. javanica and S. japonica.

FIGURE 12. Shells of S. sipho and S. javanica. A–F. S. sipho. A. Honshu, Boso Peninsula, AM C.584934 [M488]. B–C. Okinawa, AM C.584910 [M508]. D. Philippines, Cebu AM C.585120 [SK094]. E. Holotype of S. cornuta USNM5850. F. Okinawa, Tancha Bay, AM C.584925. G–H, J–K. S. javanica. G. Lectotype of P. javanica MHNG-MOLL-50923 (specimen #2). H. Paralectotype MHNG-MOLL-50923 (specimen #1). I. Paralectotype MHNG-MOLL-50917 (specimen #3, not a siphonariid). J. Timor-Leste, Dili, AM C.584795 [M434]. K. Dili, AM C.585948 [SK563]. L–O. Animals in situ. L. S. sipho, Okinawa. M. S. sipho, Okinawa [M488]. N. S. javanica, Dili, [M434]. O. S. javanica, Dili. Scale bars =10 mm.