Mipus tonganus, Oliverio, 2008

Oliverio, Marco, 2008, Coralliophilinae (Neogastropoda: Muricidae) from the southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 481-586 : 566-567

Mipus tonganus n. sp.

Figs 137, 195, 196

TYPE MATERIAL. — Holotype (dd) MNHN 20244 and 2 paratypes (dd) MNHN 20245-20246 .

TYPE LOCALITY. — Tonga, 18°39’S, 173°54’W, 281 m [BORDAU 2: stn DW 1589] .

MATERIAL EXAMINED. — New Caledonia proper. BATHUS 4: 1 dd (paratype MNHN 20246 , Fig. 196) .

stn DW 887, Passe de Duroc, 21°07’S, 164°28E, 320-344 m, 1 Tonga. BORDAU 2: stn DW 1589, 18°39’S, 173°54’W, 281 m, dd (paratype MNHN 20245, Fig. 195). 1 dd (holotype MNHN 20244, Fig. 137).

Fiji. BORDAU 1: stn CP 1506, 18°09’S, 178°37’W, 294-300 m,

DISTRIBUTION. — Known only from Tonga, Fiji and New Caledonia, empty shells in 281-320 m.

DESCRIPTION. — Shell small for the genus, holotype height 11.9 mm, width 6.5 mm, of moderate thickness, turriculate, angled at periphery, whitish.

Protoconch of 1.3 dome-shaped whorls, 680 Μm high, 780 Μm wide at base. Sculpture of small pustules scattered over entire surface. Two weak keels on final half-whorl, with a series of faint slightly opisthocline threads over each keel. Protoconch-teleoconch boundary slightly sinusigeral.

Teleoconch of 4.8 whorls. Spire high, conical, constricted at base. Periphery keeled, subsutural ramp straight or sligthly convex, whorls convex below keel. Aperture of medium size, 3.5 x 2 mm. Outer lip broken in all specimens, seemingly incised at the position of the peripheral keel. Inner lip gently curved, thin. Siphonal canal long (30% of total height), open, straight. Umbilicus closed with low siphonal fasciole. Teleoconch axial sculpture of weak undulations on first whorl, 9 broad, rounded ribs on whorls 2-4 and 8 on the last whorl, and of squamous growth lines over entire shell. Spiral sculpture of cords, covered by densely packed imbricate scaly spines each corresponding to a growth line. Two spiral cords starting immediately on first teleoconch whorl, the abapical stronger, becoming cord of peripheral keel. Additional intermediate cordlets adjoining with growth, gradually increasing in size. Cords-cordlets on subsutural ramp (excluding peripheral cord) near the end of each whorl: 2-0 on the first whorl, 2-1 on the second whorl, 3-0 on the third whorl, 3-1 on the fourth whorl, 3-1 on the fifth whorl. Cords-cordlets visible below the peripheral cord near the end of each whorl: 1-0 on the first whorl, 1-0 on the second whorl, 1-1 on the third whorl, 2-0 on the fourth whorl. Last whorl with 16 cords and 3 cordlets below peripheral cords. Suture incised, canaliculate on last whorls, undulate.

Animal and operculum unknown.

REMARKS. — The new species is nearly identical in teleoconch characters to Mipus sugitanii (Kosuge, 1985) . It differs in its paucispiral protoconch, indicating a prolonged intracapsular, probably entirely lecithotrophic development. It also has a slightly shorter spire than M. sugitanii , with fewer whorls at the same shell height. However, the holotype of M. sugitanii lacks its protoconch. Having tentatively referred material with a large protoconch to M. sugitanii (see above), M. tonganus is here described based on the material with the paucispiral protoconch.

ETYMOLOGY. — The epithet tonganus refers to the Tongan archipelago, where the type material was collected.