Leucosyrinx exulans ( Dall, 1890 )

Kantor, Yuri I., Fedosov, Alexander & Puillandre, Nicolas, 2025, Revision of the Indo-Pacific species of the genus Leucosyrinx Dall, 1889 (Neogastropoda: Conoidea: Pseudomelatomidae), European Journal of Taxonomy 999, pp. 1-126 : 60-62

Leucosyrinx exulans ( Dall, 1890)

Fig. 21A–F

Pleurotoma exulans Dall, 1890: 302 , pl. 5 fig. 7.

“ Leucosyrinx ” exulans – McLean 1971a: fig. 37 (radula of the holotype).

Type material

Holotype

GALAPAGOS IS. • SL 37 mm; off Isla de San Cristobal; 00°36′30″ S, 89°19′00″ W; depth 634 ftm (= 1160 m); Albatross , stn 2808; USNM 96499 .

Material examined (sequenced)

NEW CALEDONIA • 1 lv; 23°33′ S, 169°44′ E, depth 3014–3069 m; KANADEEP 2, stn CP5066; MNHN-IM-2019-2111 .

Description

SHELL. Medium-sized, reaching 37 mm (holotype), fusiform, thin with medium high spire, yellowishbrown, with lighter canal. Protoconch and upper teleoconch whorls eroded in available material. Teleoconch whorls roundly angulated on shoulder, last whorl in larger specimens can be nearly evenly rounded with shoulder slightly accentuated by obtuse keel. Lightly concave on upper whorls subsutural ramp, can be nearly flat on last whorl. 18–19 on penultimate and last (when present) whorl rather strong, oblique, medium broad, and rounded axial folds on shoulder of teleoconch whorls. Folds fade on subsutural ramp, not reaching lower suture, progressively weaken on last whorl towards aperture in larger specimens. Distinct spiral sculpture similar in width, low, rounded, and wavy cords. Intervals between cords do not exceed the cords’ width. Shell base strongly convex, rapidly constricting and passing into long rather narrow canal. Medium narrow, elongate-oval aperture. Shallow subsutural, broadly arcuate anal sinus extends across subsutural ramp, confluent with large forward extension of outer lip.

DNA diagnosis (based on 1 (!) cox 1 sequence)

‘G’ in site 25, ‘T’ in site 139, ‘G’ in site 439, ‘T’ in site 604.

Remarks

The species was previously known only from two lots in USNM, collected off Galapagos Is. at depths of 1160–1480 m. McLean (1971a) illustrated the radula of the holotype using light microscopy, revealing features similar to those of other species of Leucosyrinx .

A single specimen in our material was collected off southern New Caledonia at depths of 3014–3069 m. Although conchologically similar to the holotype, this specimen is significantly smaller (18 mm compared to 37 mm). Despite being collected far from the type locality, we tentatively attribute this specimen to L. exulans .

The conspecifity of our specimen with the holotype of L. exulans can only be confirmed by sequencing topotypic specimens. However, this is unlikely, as the species has not been recollected since its original description. In its current understanding, L. exulans is considered the most broadly distributed Pacific representative of the genus.

The species shows some resemblance to L. anteridion ( Watson, 1881) but differs in its darker coloration and higher spire. Another similar species is L. melvilli , distant in the phylogenetic tree, although L. melvilli is characterized by a higher spire, more numerous axial ribs, and a more abrupt narrowing of the shell base toward the canal.

Distribution

Galapagos Is., New Caledonia, 1160–3014 m.

Figures

Fig. 21. A–F. Leucosyrinx exulans (Dall, 1890). A–C. Holotype, USNM 96499, SL 37 mm. D–F. MNHN-IM-2019-2111, SL 18.1 mm. G–H. Leucosyrinx sp. 16, MNHN-IM-2009-13401, SL 25.7 mm. I–M. Leucosyrinx bernardeti sp. nov. I–K. Holotype, MNHN-IM-2013-48121, SL 34.4 mm. L–M. MNHN-IM-2007-17846, Coral Sea, 603–630 m. N–O. Leucosyrinx sp. 3, MNHN- IM-2007-42445, Philippines, 357–372 m, SL 34.1 mm. All shells at the same scale.