Siphonaria atra Quoy & Gaimard, 1833

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 : 51-54

Siphonaria atra Quoy & Gaimard, 1833

( Figs 19A–F, M–P, T–U , 21 )

Siphonaria atra Quoy & Gaimard 1833: 337 , pl. 25, figs 41–42 (type locality: Vanikoro [ Solomon Islands]).— Lamarck 1836: 560; 1839: 206; Reeve 1842: pl. 138, fig. 1; Catlow & Reeve 1845: 100; Reeve 1856: pl. 8, species 14; Jay 1850: 104; H. Adams & A. Adams 1855 (in 1853–58): 271; Hanley 1858b: 151; H. Adams & A. Adams 1863: 271; Paetel 1873: 117; 1875: 92; Brazier 1878: 134; Dunker 1882: 169; Paetel 1883: 178; 1889: 428; Hedley 1909: 369; Singleton 1937: 396; Adam & Leloup 1939: 9, pl. 2, fig. 3a,b, text-fig. 2a,b; Marcus & Marcus 1960: 109; Firth & Calaby 1974: 57; Galindo 1977: 416; Coles 1981: 11; Jenkins 1983: 29; Short & Potter 1987: 122, pl. 60, fig. 4; Wells & Bryce 1995: 113; 1996: 63; Bryce 1997: 55; White & Dayrat 2012: 61; Willan et al. 2015: 330.

Siphonaria albicante Quoy & Gaimard 1833: 335 , pl. 25; figs 38, 40 (type locality: Île de Vanikoro [ Solomon Islands] et celle de la Nouvelle-Irlande [New Ireland, PNG] au halve Carteret [Carteret Islands, PNG]).— Trew 1983: 4; White & Dayrat 2012: 60.

Siphonaria albicans Lamarck 1836: 560 .— Lamarck 1839: 485; Catlow & Reeve 1845: 99; H. Adams & A. Adams 1855 (in 1853–1858): 271; Reeve 1856: pl. 2, species 9; Hanley 1858b: 151; Chenu 1859: 206, figs 3577, 3578; H. Adams & A. Adams 1863: Paetel 1873: 117; 1875: 92; 1883: 178; 1889: 427; Galindo 1977: 416 (invalid; incorrect subsequent spelling of S. albicante ).

Siphonaria sipho — Brazier 1878: 135 (not S. sipho Sowerby I, 1823 ).

Liphonaria siquijorensis Brazier 1878: 135 (invalid; incorrect subsequent spelling; not S. siquijorensis Reeve, 1856 ).

Mestosiphon eumelas Iredale 1940: 439 , figs 5–6 (type locality: Snapper Island, North Queensland [ Australia]).— Short & Potter 1987: 122; White & Dayrat 2012: 63.

Triellsiphon acervus Iredale 1940: 439 , figs 22–23 (type locality: Canala, NC [ France]).— White & Dayrat 2012: 60.

Siphonaria (Siphonaria) eumelas — Hubendick 1946: 52; 1955: 3.

Siphonaria (Siphonaria) savignyi — Hubendick 1955: 2 (not S. savignyi Krauss, 1848 ).

Siphonaria ‘ atra group, unit 41’— Dayrat et al. 2014: 264, figs 5 V-X (in part).

Material examined. Type material. Lectotype of Siphonaria atra Quoy & Gaimard, 1833 , present designation, from l’ile de Vanikoro [ Vanikoro Island , Solomon Is]; coll. Expédition Durville, 1826 ( MNHN IM-2000-35950 , Fig. 19A ). Two paralectotypes, same data as lectotype ( MNHN IM-2000-5034 ).

Lectotype of Siphonaria albicante Quoy and Gaimard, 1833 , present designation, from l’ile de Vanikoro et celle de la Nouvelle Iriande, au havre Carteret [ Vanikoro Island , Solomon Is and New Ireland, PNG, at Carteret Harbour; thought to be Carteret Islands, PNG] ( MNHN IM 2000- 38234 , Fig. 19M ) . Paralectotype, same data as lectotype ( MNHN IM 2000-5026 , Fig. 19N ) .

Holotype of Triellsiphon acervus Iredale, 1940 from Canala , NC; coll. 1928. ( AM C.103716 , Fig. 19D ). Fifteen probable paratypes ( AM C.140260 ), same data as holotype.

Probable holotype of Mestosiphon eumelas Iredale, 1940 from Snapper Island , [near Port Douglas], N Qld [ Australia]; coll. 1928 ( AM C.103711 , Fig. 19C ). Fifteen probable paratypes ( AM C.140260 ), same data as probable holotype .

Other, non-type material. Solomon Islands: Santa Cruz Ids, Vanikoro off Sunday Reef, 11°42’S, 166°50’E ( AM C.52095 d) . NC: Tiari, 20°15.692’S, 164°24.664’E NC04-3 ( AM C.585008 p [M361]); S of Pouebo, 20°25.950’S, 164°39.251’E NC04-2 ( AM C.585005 p [M383]); Hienghène, 20°41.210’S, 164°59.108’E NC04-1 ( AM C.585003 p [M391, SK173], C.585004 p [M392]); Ponerihouen, 21°05.644’S, 165°26.646’E NC03-1 ( AM C.584977 p [SK059], C.584978 p [SK155], C.584980 p [M354], C.584981 p [M356], C.584982 p [M359] C.584983 p [M405, SK072], C.585329 p [SK040]); Poindimie, 21°55.901’S, 165°19.672’E NC03-2 ( AM C.585967 20+p, C.584993 p [M351]); Ouassé nr Canala, 21°30.346’S, 166°03.732’E NC02- 1 ( AM C.585377 10+p, C.584973 p [M373], C.584974 p [M374], C.584975 p [M376], M378, C.584976 p [M411]; Bonhomme de Bourail, La Roche Percee, 20°36.487’S, 165°27.423’E NC06-3 ( AM C.585011 p [M369]); Presqu’ile de Ouano La Foa , 20°51.434’S, 165°48.479’E NC06-4 ( AM C.595912 8p); Port Quenghi nr marina, 21°54.405’S, 166°03.880’E NC07-1 ( AM C.585018 p [M379], C.585019 p [M380]) . PNG: New Ireland, Channel betw. Manne I. and New Ireland mainland, 02°43’S, 150°43.1’E ( MNHN IM-2013-55761 p [M531], IM-2013-55762 p [M538], IM-2013-55763 p [M529], IM-2013-55764 p [M535]; Biliau I., 05°11.8’S, 145°48.2’E PM38 ( MNHN IM-2013-15193 p [M559]) . Australia, Qld: Somerset Bay, Cape York , 10°44.310’S, 142°35.637’E, Q47-2 ( AM C.585177d [R12001]); Capt Billy Landing, 11°38.019’S, 142°51.472’E, Q46-1 ( AM C.584791 p [M006, SK250]); Lizard Is, 14°40.908’S, 145°27.007’E; Q40-1 ( AM C.584801 4p); Q40-5 ( AM C.585166 p [SK218]); Cape Kimberley, 16°16.535’S, 145°28.737’E, Q35-1 ( AM C.585412 10+p, C.585167 p [M454, SK178], C.585503 p [SK179]); Low Isles, 16°23.085’S, 145°33.596’E, Q34-1 ( AM C.585704 4p, C.585160 p [M132], C.585873 p [M136]); Port Douglas , 16°28.697’S, 145°27.859’E, Q33-2 ( AM C.585158 p [M134]); Red Cliff Pt, N of Cairns, 16°41.294’S, 145°35.080’E, Q33-3 ( AM C.595969 3p); Gribble Pt Mission Bay Yarrabah, 16°53.781’S, 145°51.852’E, Q32- 1 ( AM C.585504 2p); Mourilyan Harbour, 17°35.951’S, 146°07.583’E, Q29-1 ( AM C.585410 8p, C.585534 5p, C.585151 p [M004], C.585152 p [M401], C.585153 p [SK124], C.585154 p [SK217]); Horseshoe Bay Magnetic Is, 19°06.755’S, 146°51.875’E, Q27-2 ( AM C.585345, p); Picnic Bay Magnetic Is, 19°10.757’S, 146°50.555’E, Q27-3 ( AM C.585563 9p, C.595970 2p); Mackay breakwater wall, 21°06.415’S, 149°14.033’E, Q14-2 ( AM C.585502 p; C.585639, 5p); Wreck Pt Yeppoon, 23°08.736’S, 150°45.865’E, Q08-4 ( AM C.585562 3p, C.585132 p [M080]); Bagara Hervey Bay , 24°49.180’S, 152°28.011’E, Q06-1 ( AM C.585699 8p); Drury Pt Scarborough, 27°12.255’S, 153°07.022’E, Q03- 7 ( AM C.585685 7p) . NT: S Turtle Beach 12°18.852’S, 136°55.959’E NT04-2 ( AM C.585666 6p, C.585073 p [M013], C.585074 p [M096]; Cape Wirawawoi Nhulunbuy, 12°09.513’S, 136°46.904’E NT05-A ( AM C.585593 4p); Smith Pt, 11°07.360’S, 132°08.134’E NT21-2 ( AM C.585667 6p); Nightcliff Darwin, 12°22.836’S, 130°50.402’E NT23-1 ( AM C.585088 d) . WA: Tait Point 1 Mission Bay, 14°05.442’S, 126°41.143’E, WA04-1 ( AM C.584716 5p; WAM S74089 5p); Walsh Point, 14°33.998’S, 125°51.060’E, WA13-1 ( AM C.584697 3p; WAM S74090 3p); Caffarelli Is, 16°01.991’S, 123°18.625’E, WA19-1 ( AM C.584717 5+p, C.585012 p [SK034], WAM S74092 5p); Conilurus Is, 16°08.872’S, 123°35.205’E, WA18-2 ( AM C.584721 5p, WAM S74091 4p); Catamaran Bay formal, 16°27.622’S, 123°00.242’E, WA22-3 ( AM C.584703 4p, WAM S74094 3p); Catamaran Bay , 16°27.622’S, 123°00.242’E, WA22-1 ( AM C.584737 27p, C.585300 p [SK189], WAM S74093 5p); Gantheaume Point, 17°58.384’S, 122°10.677’E, WA26-2 ( AM C.584718 5p; WAM S74095 5p) .

Taxonomic remarks. The largest syntype is herein designated as the lectotype of Siphonaria atra ( MNHN IM-2000-35950) to ensure an unambiguous identity of this species and for the stabilisation of the name (Art. 74.1 of the Code). While topotypic specimens from Vanikoro are currently unavailable, the identity of S. atra ( Fig. 19B ) and its junior synonyms Triellsiphon acervus ( Fig. 19F ) and S. albicante ( Fig. 19O ) are each established based on the examination of specimens from NC that closely match the types. Furthermore, our delineation of this species is also based on comparative analyses of the morpho-anatomy and mitochondrial genetics of freshly collected topotypes of M. eumelas ( Fig. 19P ) and Triellsiphon acervus ( Fig. 19E ) as well as geographic series of additional specimens (Table S1).

The shells figured as ‘ Siphonaria atra ’ by Reeve (1856: pl. 3, fig. 14) exhibit a mixture of features typical for two species, S. sirius and S. atra . The description in Reeve mentioned features characteristic of S. sirius (i.e., shell pattern and single siphonal rib) but not S. atra . Furthermore, the initial two locations listed in Reeve (1956) are within the known distribution of S. sirius and well outside the known distribution of S. atra . Only Vanikoro, the type locality, is within the range of S. atra . Reeve (1956) incorrectly treated S. coreensis as a synonym of S. atra .

In several cases, the details of type locality in the original designations of Iredale (1940), differed from what appeared on the specimen labels. Iredale (1940: 438) specified ‘type’ in the original descriptions for T. acervus and M. eumelas . The figured specimens of T. acervus ( Iredale, 1940: pl. 34, figs 22–23; Fig. 19D herein) and M. eumelas (pl. 34, figs 5–6; Fig. 19C herein) are considered as probable holotypes. Hubendick (1946: 50) listed amongst a number ‘transitional’ forms in an ‘Indian-West Pacific form-group’ a ‘ S. zanda <> S. atra ’ form. The figured specimen ( Hubendick 1946: 50, pl. 5, figs 3–4) is as a specimen of S. atra . Overall, it appears that the interpretation of S. atra in Hubendick (1946: 52) is uncertain. The specimens assigned to this species by him were from Mindanao, the Java Sea, and Osagawara [= Ryukyu, Japan] ( Hubendick 1946: pl. 4, figs 5–7). None of these localities are within the known distribution of S. atra ( Fig. 16 ) and therefore these are likely specimens of S. alba and S. subatra , respectively. Similarly, ‘ S. atra ’ recorded from Nagasaki in Lischke (1871: 105) and from Okinawa in Kuroda (1960: 43) are likely S. subatra . A record of ‘ S. albicans ’ in Hutton (1880: 36) from NZ is likely based on a misidentification of S. australis .

Mestosiphon eumelas has been synonymized with S. atra by Hubendick (1946: 52, 1955: 128), which is followed herein. Cernohorsky (1972: 210) also treated M. eumelas a synonym of S. atra ; however, his figure of ‘ S. atra ’ (pl. 60, fig. 1, Naviti Is, Fiji) shows a specimen of S. vudaensis sp. nov. Morrison (1972: 56–58) treated S. atra as a synonym of S. laciniosa based on similarity in the shell and for a ‘common reproductive development’. This synonymy is rejected herein based on examination of type specimens and comparative morpho-anatomy. The unfigured records of ‘ S. atra ’ in Chambers (1980: 141, 143), Christiaens (1980a: 78) and Chambers, McQuaid & Kirby (1998: 51) from Hong Kong are here attributed to either S. alba or S. sirius .

External morphology ( Fig. 19U ). Foot sole, foot wall, foot edge, cephalic folds and pneumostomal lobe evenly cream; mantle thick translucent in larger specimens, thin in smaller specimens, edge thickened, whitish, lobed, with very light black pigmentation at mantle edge aligning with large primary rib interstices; genital pore inconspicuous, located on foot wall to right anterior of right cephalic fold; two small black epithelial eye spots centralised on two centrally touching, centrally black pigmented cephalic folds; pneumostomal lobe long, under the mantle, unpigmented, behind right cephalic fold.

Shell ( Figs 19A–F, M–P, T ; Table S9). Shell morphology displays wide intraspecific variability, medium sized (max sl mean = 21.7 mm, SD = 3.3 mm, n = 23), ovate; height low to medium; apex offset sightly posterior and central, apical sides convex, protoconch direction homostrophic (n = 3) shell whorl dextral; growth striae prominent in bands, shell thickness thick; exterior uneven, dark purple brown to pale tan, radial colour banding often present, protoconch area pale, central band darker and shell edge dark brown; rib count (mean = 49, SD = 6, n = 23), primary rib ridges pale, ribs fairly straight, increasingly raised and strongly protrude beyond shell lip (often> 1mm) to unevenly scallop and corrugate the edge; siphonal ridge often greatest protrusion, formed by paired primary ribs; 1–2 finer interspersed secondary ribs between primary, rib interstices darker. Interior shell margin dark chocolate brown to white, white rays on shell margin aligned under primary/secondary ribs dark chocolate brown to white, siphonal groove distinct, often same colour as shell margin, white forms with fringing dark brown markings; spatula dark chocolate brown to golden brown even whitish; ADM scar distinct, CMS straight, darker than shell lip; thickening of shell lip common, overcoats brown markings on shell margin with white, infills and reduces lip scalloping, and often spatula becomes whitened.

Reproductive system ( Fig. 21 ; n = 19). HG / AG / MG complex positioned within right side of coelom, against foot wall over foot muscle, under the respiratory cavity; epiphallic parts positioned between BM and RAM; GA small, with singular GP through foot wall; AO large, broad, bluntly pointed, joined to upper GA; ED short, broad, centrally slightly bent, joins to side of GA; GA, AO, ED all white muscular fibrous tissue; EG large, longer than ED, soft whitish tissue, folded, joins ED; single very broad flagellum (F1), similar length and width to ED, appears as an extension of ED. BD and CD connect side-by-side into GA between ED join and GP, both ducts short, straight, smooth, thickened, whitish, featureless, pass closely together through RAM ( BD over CD) into soft white folded tissues of MG; MG / AG complex relatively large; CD connecting to ducts, BC embedded in folds of AG / MG complex close to embedded blackish SV; BD with short distal twisted loop, similar thickness but longer than CD; BC relatively small, bulbous, thin whitish translucent test, HD short, wide, coiled, links ducts in soft white folded tissues of AG to yellowish granulated HG; outer edge of MG lobbed; AG usually larger than HG; genital pore inconspicuous, located on foot wall posterior to right cephalic fold.

Spermatophore ( Figs 21C, G ). Over half of length comprises a translucent cylindrical head section, tip bluntly rounded, central white core; flagellum very thin, transparent, tapering to a thread-like end; both sections smooth, featureless; test thin, translucent (head length = 10.58 ± 1.73 mm; head width = 188 ± 44 μm n = 2; flagellum width = 33 μm, n =1), possibly longer as flagellum appears incomplete); very short taper region into the filamentous transparent flagellum; three and 5 SPMs respectively tightly coiled and embedded in brown gelatinous mass in BC of 2 specimens [M391, M380].

Radula. Dentition formula: 35:1:35 ( Hubendick 1946: 52).

Comparative remarks. Siphonaria atra ( atra group, unit 41) forms a clade with unit 40 ( S. hienghenensis sp. nov. + unidentified species from PNG and Qld) and S. alba (unit 39) ( Figs 1 , 2 ). It differs from these two units by COI distances of ≥ 11.1% ( S. hienghenensis sp. nov.) and ≥ 8.3% ( S. alba ) (Table S3). The maximum distance among sequences in unit 41 (= S. atra ) is 12.8% (Tabe S2). This is the highest intraspecific genetic divergence observed among all Siphonaria species examined herein. This exceptionally high divergence can partly be attributed to a single GenBank sequence from PNG ( UF 332973), which is considered to likely represent a separate, unidentified species. When this sequence is excluded from S. atra , the maximum COI distance within unit 41 is 9%.

Siphonaria alba is indeed morphologically similar; however, it has a shell with a slightly less scalloped edge, a longer ED, larger BC, and longer SPM. Both species occur in sympatry in Timor-Leste and Western Australia. Siphonaria hienghenensis sp. nov. has a paler, grey-brown shell with a weaker scalloped edge, and a smaller AO. Both species are found in sympatry in New Caledonia. Throughout the range of S. atra we found twenty-two congeners within partly sympatric distributions. Eight congeners are sympatric with S. atra in NC: Siphonaria namukaensis sp. nov. has a smaller, paler, slightly taller shell with a weaker scalloped edge, a broader ED, and a longer SPM. Siphonaria normalis has a smaller, paler shell with a less prominent siphonal ridge and a weaker scalloped edge, a smaller AO and larger BC. Siphonaria ouasseensis sp. nov. has a smaller more evenly ribbed shell with a stronger offset apex, weaker scalloped edge, and a smaller AO. Siphonaria caledonica sp. nov. has a smaller shell with a greater offset apex and weaker scalloped edge, a longer ED, and longer SPM. Siphonaria bourailensis sp. nov. has a smaller shell with a greater offset apex and weaker scalloped edge, and a shorter F1. Siphonaria poindimiensis sp. nov. has a smaller, taller, and darker shell with external patterning, a larger, broader ED, and a longer SPM. Siphonaria viridis has a smaller, taller, and darker shell with external patterning, a larger, broader ED, and longer SPM.

Ten congeners are sympatric with S. atra in tropical Qld, NT and WA, Australia (along with S. normalis and S. viridis ). Siphonaria costellata sp. nov. has a shell with a greater offset apex, weaker scalloped edge, a smaller AO, longer BC, and shorter BD. Siphonaria denticulata has a larger, paler, taller shell with narrower ribbing and without a scalloped edge, a smaller AO, and longer SPM. Siphonaria gemina sp. nov. has a smaller, paler shell with a weaker scalloped edge, a smaller AO, and a shorter BD. Siphonaria jiigurruensis sp. nov. has a smaller, taller shell with a greater offset apex, patterned exterior, a longer, broader ED, more bulbous AO, and a longer SPM. Siphonaria oblia has a far smaller, fragile and taller shell with a well offset apex, weaker scalloped edge, a longer, wider ED and smaller F1 ( Jenkins, 2018: 278, figs 3C–D). Siphonaria opposita has a lower shell with paler interior, weaker scalloped edge, a larger BC, and longer ED and BD with bursal loop. Siphonaria restis sp. nov. has paler, taller shell with raised and uneven ribbing, a weaker scalloped edge, a smaller AO, longer ED and larger BC. Siphonaria scabra has a paler, taller shell with a weaker scalloped edge, a smaller AO, longer ED and larger BC. Siphonaria zelandica has a smaller, lower, thinner, paler shell with a weaker scalloped edge, a smaller AO, without distal loop on BD, and a shorter drop-like SPM. Siphonaria forticosta sp. nov., along with S. alba , is sympatric in TL. It has a paler shell with weaker splayed siphonal ridge, a smaller AO, and larger BC. For a comparison with S. javanica found in sympatry in PNG refer to comparative remarks under that species.

Wide intraspecific variability occurs in shell morphology of S. atra (particularly characteristics of shell thickness, ribbing and interior colouration) irrespective of shell size or geographical distribution. Variability in shell morphology ranges from a dark (i.e., S atra , S. eumelas ) to pale (i.e., S. albicante , T. acervus ) forms. The RS anatomy of both forms is consistent, however ( Figs 21A, F dark shell form, Fig. 21B , pale shell form).

Shell geometry, sculpture and colouration of S. atra resemble those of 13 other species in the atra group in the IWP region; S. subatra (unit 38), co-occurring S. forticosta sp. nov. (unit 71), S. hienghenensis sp. nov. (unit 40) and S. bifurcata (unit 45), S. denticulata (unit 33), S. scabra (unit 50), S. pravitas sp. nov. (unit 51), S. crenata (unit 43), S. tenebrae sp. nov. (unit 96), S. vudaensis sp. nov. (unit 37), S. alba (unit 39) and S. sirius (unit 31). However, all these species exhibit differences in the structure of RSs, some have finer shell features and all of them are genetically well-differentiated. Figured specimens of ‘ S. atra’ in Adam & Leloup (1939: 9, pl. 2, figs 3a, b) match the shell size, sculpture, and ribbing of S. atra , and align with its distributional range and radula dentition count (p. 10, text fig. 2a, b). Figured specimens of ‘ S. (S.) atra ’ in Hubendick (1946: 91, pl. 4, fig. 5–7) from Mindanao are likely specimens of S. alba , not of S. sirius (with a single siphonal rib) or S. atra (with narrower, less protruding primary ribbing). A shell figured as S. atra in Tan & Chou (2000: fig. 117) corresponds with features of S. alba (i.e., shell exterior ribbing, interior colouration). Records of ‘ S. atra ’ in Habe (1962: 96, pl. 44, fig. 17; 1964: 145, pl. 44, fig. 17) from Honshu, subsequently referenced also by Maes (1967: 119) are likely misidentifications of S. subatra . We could not confirm any records of S. atra from Japan or the Philippines. The records of ‘ S. atra ’ in Maes (1967: 119) and Wells (1994: 18) are here attributed to S. alba . Way & Purchon (1981: 321) recorded ‘ S. atra ’ from West Malaysia and Singapore, and Tan & Low (2014: 267) recorded ‘ S. atra ’ from CKI, however, we are unable to confirm the occurrence of S. atra in these regions. Figured specimens of the ‘ atra group, unit 41’ in Dayrat et al. (2014) from Lizard Island (fig. 5W) and PNG (fig. 5X) are morphologically consistent with S. atra .

Distribution and habitat. Recorded from throughout large parts of Tropical IWP including Santa Cruz Islands, American Samoa, Solomons Islands, NC, PNG, northern Australia (Cape York Peninsula through to Kimberley, WA), and Timor-Leste ( Fig. 16 ). In this study found to be common on exposed rocky shores across upper littoral levels ( Fig. 19Q ).

Figures

FIGURE 1. Maximum Likelihood phylogram based on analyses of a concatenated sequence data set of 16S and COI. Branches are collapsed at the species level. Branch labels give unit numbers and accepted species names. Numbers on branches indicate branch support employing 10,000 ultrafast bootstraps.Available genus-group names are shown next to their type species. Scale bar indicating modelled sequence divergence.

FIGURE 2. Maximum Likelihood phylogram (partial, species not collapsed). Clades G–I (atra group) 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 (seeTables 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 spread over two pages.

FIGURE 16. Known occurrence records of S. obliquata, S. radiata, S. diemenensis, S. australis, S. atra and S. denticulata

FIGURE 19. Shells of S. atra and S. denticulata. A–F, M–Q, T–U. S. atra, A. Lectotype MNHN-IM-2000-35950. B. NC, Hienghène, NC, AM C.585003 [M391, SK173]. C. Probable holotype of Mestosiphon eumelas AM C.103711. D. Probable holotype of Triellsiphon acervus AM C.103716. E. NC, Ponerihouen, TS of T. acervus AM C.584983 [M405, SK072]. F. NC, Port Quenghi, AM C.585018 [M379]. M. S. albicante lectotype MNHN IM-2000-38234. N. Paralectotype IM-2000-5026. O. NC, Ouassé, TS of T. acervus AM C.584976 [M411, SK061] P. Qld, Cape Kimberley, TS of M. eumelas AM C.585167 [M454, SK178]. T. WA, Catamaran Bay, AM C.585300, protoconch. Q, U. In situ, animal NC, Port Quenghi, NC07-1. G–L, R. S. denticulata. G. Lectotype MNHN-IM-2000-35951. H. NSW, Kiama AM C.585333 [SK043]. I. Holotype of S. currumbinensis MV F.15562. J. NSW, Currumbin, TS of S. currumbinensis AM C.585123 [M074, SK033]. K. Probable holotype of Ellsiphon marza AM C.103715. L. Qld, Yeppoon, TS of E. marza AM C.584743 [SK030]. R. Animal. Unlabelled scale bars = 10 mm.

FIGURE 21. Reproductive morphology of S. atra. A. NC, La Roche Percee, AM C.585011, dark shell form [SK174]. B–C. NC, Ponerihouen, AM C.584978, pale shell form [SK155]. D. Qld, Cape Kimberley, TS of M. eumelas AM C.585167 [M454, SK178]. E. WA, Caffarelli Is, AM C.585012 [SK034]. F–G. NC, Hienghène, AM C.585003, dark shell form [M391, SK173]. Unlabelled scale bars = 1 mm.