Siphonaria poindimiensis, B. W. Jenkins & Köhler, 2024

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 : 186-188

Siphonaria poindimiensis sp. nov.

( Figs 76A–C, J–K, 77A–B)

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

Siphonaria ‘ laciniosa group, unit 19’— Dayrat et al. 2014: 261, fig. 4A (in part).

Material examined. Type material. Holotype, from Poindimie, 21°55.901’S, 165°19.672’E, NC; coll. B.W. Jenkins, NC03-2, 23 Oct 2018 ( AM C.584999 [M352, SK128], Fig. 76A) . Paratypes, same data as holotype ( AM C.585837 p [SK129], Fig. 76B); Tiari, 21°05.644’S, 165°26.646’E, NC; coll. B.W. Jenkins, NC04-3, 27 Oct 2018 ( AM C.585002 p [SK261], Fig. 76C) .

Other, non-type material. NC: Tiari, 21°05.644’S, 165°26.646’E, NC04-3 ( AM C.585010 p [SK262]); Poum 2, 20°13.754’S, 164°01.699’E, NC05-3 ( AM C.585998 6p) .

Taxonomic remarks. The record of S. laciniosa from NC ( Hubendick 1946: 47) possibly refers to this species.

External morphology. Foot sole grey; foot wall evenly dark cream, paler to foot edge; irregular black pigmented blotches on foot wall; cephalic folds thick narrow; black pigmentation darker over centre of cephalic folds, paler to foot; mantle wide thin with heavy broad lobes, wider extended at anterior, edge thickened with black pigmentation aligning with rib interstices; pneumostome small, under mantle.

Shell ( Figs 76A–C, J; Table S9). Medium to large sized (max sl mean = 12.9 mm, SD = 1.6 mm, n = 3), elongate ovate; medium to tall; apex strongly offset to left posterior, apex hooked, curved to posterior; apical sides strongly convex, weakly concave to straight on posterior side; shell growth often irregular; protoconch direction central to homostrophic (n = 2, Fig. 76J) shell whorl dextral; growth striae prominent, shell thick, exterior uneven; rib count (mean = 45, SD = 6.2, n = 3), marked difference between primary and secondary ribs, 9–11 primary ribs solidly raised, rounded ridge, weakly crooked, pale white, strongly protrude beyond shell lip to unevenly scallop and corrugate the shell edge; paired ribs form siphonal ridge; areas of finer secondary ribs dark brown/black between primary ribs, often with narrow white flecks/bands. Interior shell lip and lower margin white, changing to dark brown in spatula; dark brown bands extending from shell edge to spatula under secondary ribs and rib interstices; siphonal groove distinct, same colour as shell edge; spatula evenly dark chocolate; ADM scar distinct, CMS straight; thickening of shell lip not apparent, the number of primary ribs may be reduced to 7 in one specimen ( Fig. 76C).

Reproductive system ( Fig. 77A; n = 2). Positioned within coelom under the respiratory cavity, hermaphroditic complex ( HG, AG and MG) to posterior against right foot wall and over foot sole, epiphallic parts positioned to anterior between RAM and over BM; AO very large, elongated, centrally bent, bluntly bulbous to pointed, merges to upper part of indistinct GA, singular very small GP; ED relatively long, broad, twisted, longer than AO, joins to lower side of GA; GA, AO, ED all white muscular fibrous tissue; EG soft whitish, slightly folded, smaller than AO; single long blunt twisted flagellum (F1); BD and CD jointly but opposing connections to GA between AO and GP; BD long narrow with prominent distal loops (may loop behind ED) and MAs to inner body wall; CD broad short, wider than BD; both ducts smooth and pass closely together through outer side of RAM ( BD over CD); CD connects into MG; BD connects to small bulbous BC with thin translucent test, embedded in folds of MG close to embedded SV; HD short, thick, white, coiled, links AG to smaller yellowish granulated HD; MG and AG folded, soft white tissue.

Spermatophore ( Fig. 77B). Test thin, translucent (length 4.11 mm, n = 1), head bulbous, tip bluntly rounded, containing a white gelatinous mass; taper region into the filamentous transparent flagellum is extended; both sections smooth, featureless; head longer and much thicker than flagellum (head length = 3.29 ± 0.49 mm, ~72% of SPM length, head width = 74 ± 8 μm, flagellum width = 1 μm, n = 2); SPM tightly coiled in a brown gelatinous mass.

Comparative remarks. In our mitochondrial phylogeny ( Figs 1, 3), S. poindimiensis sp. nov. ( laciniosa group, unit 19) is the sister species of S. tanchaensis sp. nov. (unit 20). Both species differ by COI distances of ≥ 21.8% (Table S6). We found S. poindimiensis sp. nov. in sympatry with seven congeners in NC. For comparisons with S. atra , S. namukaensis sp. nov., S. normalis , S. bourailensis , S. hienghenensis sp. nov., S. caledonica sp. nov., and S. viridis refer to comparative remarks under these species.The external morphology of S. poindimiensis closely resembles that of S. vudaensis sp. nov. (unit 37) from Fiji. The specimen figured as ‘ laciniosa group, unit 19’ by Dayrat et al. (2014: fig. 4A) exhibits morphological characters typical for S. poindimiensis sp. nov.

Distribution and habitat. Recorded as endemic to eastern coast of NC, Pacific Ocean ( Fig. 78). In this study, found on moderately exposed rocky shores, at upper and mid littoral levels ( Fig. 76K).

Etymology. For the type locality, Poindimie, NC.