Granulifusus discrepans (Kuroda & Habe, 1961)

Figs 3 A–E, 4A

Pseudolatirus discrepans Azuma, 1960: 45 (ex Kuroda MS). nomen nudum.

Pseudolatirus discrepans – Kuroda & Habe in Habe 1961: 66, pl. 33, fig. 6. — Habe 1962: 102, pl. 33, fig. 6. — Higo, Callomon & Gotō 2001: 87, fig. G3002 (holotype illustrated). — Mallard & Robin 2017: 152.

Granulifusus discrepans – Poppe 2008: pl. 343, fig. 1.

Molecular diagnosis

A molecular diagnosis is given in Table 2.

Type material

Holotype

JAPAN: off Cape Ashizuri, southwestern Shikoku (NSMT Mo 40377) (not seen).

Sequenced material

SOLOMON SEA: 1 lv, MADEEP, stn CP4337, SE Ainto Bay, New Britain, 06°07’ S, 149°17’ E, 287– 447 m (MNHN IM-2013-46327).

PHILIPPINES: AURORA 2007, 1 lv, stn CP2657, 16°01′ N, 121°51′ E, 342–358 m (MNHN IM-2007- 34604); 2 lv, stn CP2673, 15°01′ N, 121°45′ E, 431–493 m (MNHN IM-2007-34583, MNHN IM-2007- 34488); 2 lv, stn CP2732, 15°27′ N, 121°36′ E, 556 m (MNHN IM-2007-34580, MNHN IM-2007-34581).

Other examined material

PAPUA NEW GUINEA: 1 lv, PAPUA NIUGINI, stn CP3949, 5°12′ S, 145°51′ E, 380–407 m (MHNH 2013-15374, not sequenced); 1 lv, stn CP4023, 5°22′ S; 145°48′ E, 340–385 m (MNHN IM-2013-9777, not sequenced).

Description

Shell large, with multispiral protoconch of 2.75 conical, smooth, convex, grayish whorls, last ¼ whorl with 6–7 rounded axial riblets progressing in strength, protoconch/teleoconch boundary without varix, defined by appearance of spiral sculpture. Protoconch diameter 960 µm, exposed height 890 µm (Fig. 3E). Teleoconch with regularly convex whorls, upper ones slightly angulated, with long slightly sinuous to nearly straight siphonal canal; aperture in young specimens with 3–4 plicae, in adult with a single columellar plica, delimitating siphonal canal, and sometimes with indistinct parietal tooth. Axial sculpture of distinct axial ribs, 7–8 per whorl on upper whorls, obsolete on posterior whorls in shells over 50 mm. Spiral sculpture of 2–3 raised cords on periphery of upper whorls and numerous thin riblets of even strength. On posterior whorls, cords obsolete and some riblets more pronounced. Background colour tan, with darker brown spiral bands along suture.

Radula (MNHN IM-2013-46327, SL 18.2 mm, Fig. 4A) 1.83 mm in length (32% of AL without canal), of 75 transverse rows of teeth, of which 35 nascent. Radula narrow, distance between outer edges of lateral teeth about 65 µm (1.12% of AL). Lateral teeth medium broad, arcuate, with attenuated outer anterior corner, producing short ‘handle’. Lateral teeth with five closely spaced, slightly curved cusps similar in length, small outermost cusp (seen on lower right lateral tooth on Fig. 4A), and much smaller but distinct innermost cusp. Central tooth small, very narrow, trapezoid, with three subequal cusps. Narrow but distinct transverse folds of radular membrane situated serially between rows of lateral teeth. Couto (2016: fig. 58) illustrated the radula of an adult specimen (SL 66 mm). The lateral teeth were relatively much broader, with 6 main cusps nearly identical in size and an additional innermost cusp. The radula had a similar width (1.1% of AL, measurements taken from photo) to the one studied herein; the differences in teeth morphology can possibly be explained by ontogenetic variability.

Distribution

From Japan throughout the East China Sea to the Philippines and the Solomons.

Remarks

This is the largest species of Granulifusus, which attains a shell length over 90 mm (http://www.conchology.be, last accessed 6 Mar. 2017). Due to the ontogenic change in sculpture pattern, the shell morphology differs from that in other Recent members of the genus, but the radula is similar. Young specimens bear a superficial resemblance to specimens of the Miocene species Pseudolatirus bilineatus of similar size (compare Fig. 3C, G with Fig. 3 D’, F’).