Hidden in plain sight: Systematic review of Indo-West Pacific Siphonariidae uncovers extensive cryptic diversity based on comparative morphology and mitochondrial phylogenetics (Mollusca, Gastropoda) Author Jenkins, Bruce Australian Museum, 1 William Street, Sydney, NSW 2010, Australia Author Köhler, Frank Australian Museum, 1 William Street, Sydney, NSW 2010, Australia frank.koehler@austmus.gov.au text Megataxa 2024 2024-10-23 13 1 1 217 journal article 308485 10.11646/megataxa.13.1.1 5fb5ad02-791f-4bdc-a664-9f8adcba2a43 2703-3090 14984186 Siphonaria itampoloensis sp. nov. ( Figs 61F–G , 62A ) Siphonaria ‘ laciniosa group, unit 25’— Dayrat et al. 2014: 261 (in part). Material examined. Type material. Holotype , from Itampolo , SW Madagascar ; coll. O. Griffiths , MA09_1b, July 2018 ( AM C.584955 [M273], Fig. 61F ) . Paratype , same data as holotype ( AM C.584956 p [M274], Fig. 61G ) . External morphology . Foot sole, foot wall, cephalic folds and pneumostomal lobe evenly cream in colour, paler to foot edge; mantle thin, translucent, wider than foot wall, strongly lobed with thickened edge, faint brown pigmentation on mantle edge; no black pigmentation; pustules prominent on foot wall; two black ‘Eye’ spots prominent centrally on thickened cephalic lobes; pneumostome fold prominent. Shell ( Figs 61F–G ; Table S9). Small sized (max sl mean = 9.07 mm , SD = 0.35 mm , n = 2), circular ovate; height tall; apex offset central, apical sides convex, protoconch direction central to weakly homostrophic (n = 1), shell whorl dextral; growth striae distinct, exterior uneven, shell thickness thick; rib count (mean = 25, SD = 1.0, n = 2), predominance of pale white primary ribs, crooked, often discontinuous to shell lip, single secondary ribs may develop between primary ribs, rib interstices dark brown, ridges rounded, increasingly raised and protrude slightly beyond uneven weakly scalloped and strongly corrugated shell edge; siphonal ridge indistinct. Interior shell lip and margin dark chocolate brown with white rays aligning under primary/secondary ribs, fading to prominent thin ADM scar; spatula whitish to golden tan; siphonal groove indistinct, CMS convex; thickening or whitening of shell lip not observed. Reproductive system ( Fig. 62A; n = 2). Positioned within coelom under the respiratory cavity, hermaphroditic glands positioned to posterior against right foot wall and over foot sole, epiphallic parts lay over BM to side of RAM . ED distinct entry to top of GA ; AO indistinct, part of GA , GA / AO large, elongated, weakly bent; ED thick, elongated, slightly twisted; AO , GA and ED all muscular white tissue; EG large, folded, soft white tissue; single looped thick blunt flagellum F1 appears as extension of ED at EG join; BD and CD with bulbous ends connect side by side into GA , both ducts smooth, short, broad, slightly bent, pass together through RAM ( BD over CD ) connecting into MG ; BC white opaque test, relatively small, bulbous, embedded along with part of BD in soft white folds of MG ; HD long, narrow, coiled, links soft white folded AG to small yellowish granulated HG ; AG larger than HG , both with outer sides curved reflecting the close positioning to curvature of inner foot wall at right posterior quarter of coelom; SV embedded in AG close to BC . Comparative remarks. In our mitochondrial phylogeny, S. itampoloensis sp. nov. ( pectinata group, unit 81) is the sister species of S. carbo ( Figs 1 , 4 ) Both species differ from each other by COI distances of ≥ 5.1% (Table S8). Morphologically, S. carbo has a darker, more finely ribbed, grey/brown shell, a longer, wider BD and larger BC . We have found S. itampoloensis sp. nov. in sympatry with two congeners in Madagascar : Siphonaria striata sp. nov. has a lower shell with more raised ribs, a prominent siphonal ridge and posteriorly offset apex, a larger AO , a longer BD with distal and bursal loops, and a shorter F1. For comparison with S. madagascariensis refer to comparative remarks under that species. Siphonaria itampoloensis sp. nov. differs from other members of the pectinata group, such as S. asghar , S. capensis , and S. pectinata (unit 4), by having a taller shell, more prominent shell ribbing, distinct shell interior colouration, and larger and thicker epiphallic parts. Distribution and habitat. Recorded exclusively from Madagascar , Indian Ocean ( Fig. 60 ). In this study, found on intertidal rocks, on inner lagoon shores. Etymology.Named after the type location of Itampolo, SW Madagascar , Indian Ocean.