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

Siphonaria nusalikensis View in CoL sp. nov.

( Figs 63L View FIGURE 63 , 64E View FIGURE 64 )

Material examined. Type material. Holotype, from NW side of Big Nusa Island , 02°34,1’S, 150°46,7’E, New Ireland, PNG; coll. KAVIENG 2014 expedition, KM21, 28 Jun. 2014 ( MNHN IM-2013-55334 [M532], Fig. 63L View FIGURE 63 ). GoogleMaps

External morphology (preserved). Foot sole, foot wall, cephalic folds and pneumostome cream, paler to foot edge; mantle translucent, edge thickened strongly lobed with dark/black pigmentation on mantle edge aligning with rib interstices, faint pigmentation over cephalic folds.

Shell ( Fig. 63L View FIGURE 63 ; Table S9). Small sized (max sl = 4.76 mm, n = 1), circular ovate, height tall; apex weakly offset to posterior and left, apical sides convex except posterior which is concave; protoconch hooked to posterior, direction heterostrophic (n = 1), shell whorl dextral, shell thin; growth striae indistinct; multiple radial colour bands, protoconch area dark brown, central bands pale to dark, shell fringe pale brown; rib count (29, n = 1), predominance of primary ribs, few secondary ribs, weakly raised, off white and rounded, broaden to shell edge; paired primary ribs form siphonal ridge, ribs ends protrude weakly at shell lip, shell edge weakly scalloped and corrugated; rib interstices indistinct, darker. Interior shell margin to spatula mottled dark chocolate brown; outer shell margin paler with light brown rays aligning under ribs; siphonal groove distinct, same colour as spatula, darker than margin; ADM scar indistinct, CMS convex; no thickening of shell lip noted.

Reproductive system ( Fig. 64E; n View FIGURE 64 = 2). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity; epiphallic parts positioned between RAM and BM. GA small, with singular GP through foot wall; AO small, bulbous, tip blunt, joined to upper GA; ED (incomplete) broad, joins to side of AO and GA; GA, AO, ED all white muscular fibrous tissue; BD and CD connect closely together into GA below AO junction, both long, narrow, slightly bent, pass closely together outside RAM ( BD over CD) into soft white folded tissues of MG; BD smooth, featureless; CD with short lobed mid-section; CD connecting to large MG / AG complex; BC relatively small, elongate, thin whitish translucent test, embedded in MG / AG folds close to embedded SV; BD without distal loop or MA; HD small, coiled, links ducts in soft white folded tissues of AG to yellowish granulated HG; outer edge of MG lobed; AG larger than HG, sides match curvature of inner foot wall.

Comparative remarks. In our mitochondrial phylogeny ( Figs 1 View FIGURE 1 , 3 View FIGURE 3 ), S. nusalikensis sp. nov. ( plicata group, unit 89) is the sister species of a clade comprising S. guamensis (unit 70) and an unidentified species from Rarotonga known only from one DNA sequence (unit 17). Siphonaria nusalikensis differs from these species by genetic distances in COI of 11% ( S. guamensis ) and 13.3% (unit 17) (Table S7). We found S. nusalikensis sp. nov. in sympatry with three congeners at New Ireland, PNG: For comparisons with S. normalis and S. viridis refer to comparative remarks under these species. Siphonaria recurva sp. nov. differs in having a larger shell with a less offset apex, a more prominent siphonal ridge and stronger edge scalloping, a similar BD, but with distal loop and a larger BC.

Distribution and habitat. Recorded as exclusive to Nusalik Island (Big Nusa Island), Kavieng, PNG ( Fig. 67 View FIGURE 67 ). In this study, found on rocky shores, intertidal.

Etymology. Named after the type locality of Nusalik Island (Big Nusa Island), Kavieng, PNG.