Cylichnium nanum, Valdés, 2008

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 704-705

publication ID	978-2-85653-614-8
persistent identifier	https://treatment.plazi.org/id/03D087B2-FF91-BE58-FEE3-7515F28DFAD1
treatment provided by	Felipe
scientific name	Cylichnium nanum
status	sp. nov.

Treatment

Cylichnium nanum View in CoL n. sp.

Figs 55G, H, 58

TYPE MATERIAL. — Holotype MNHN 20367 and 16 paratypes MNHN 20368-20377, 5 paratypes LACM 2998 View Materials .

TYPE LOCALITY . — Vanuatu, 16°54’S, 168°20’E, 459-488 m [MUSORSTOM 8: stn DW 1045 ] GoogleMaps .

MATERIAL EXAMINED. — Philippines. MUSORSTOM 3: stn m, 1 dd, paratype ( MNHN 20372 View Materials ) stn DE 696, Passe de Hien- DR 94, 13°47’N, 120°03’E, 842 m, 1 dd, paratype ( MNHN ghène, 20°34’S, 164°57’E, 497-520 m, 1 dd, paratype ( MNHN 20368 View Materials ); stn CP 106, 13°47’N, 120°30’E, 640-668 m, 5 dd, pa- 20373); stn DE 697, 20°34’S, 164°58’E, 570-650 m, 1 dd, pararatypes ( LACM 2998 View Materials ). type ( MNHN 20374 View Materials ) GoogleMaps . — BATHUS 2 : stn CP 743, Passe de Bou- Indonesia. CORINDON: stn B 247, Makassar , 00°55’N, lari, 22°36’S, 166°26’E, 713-950 m, 5 dd, paratypes ( MNHN 119°26’E, 520 m, 1 dd, paratype ( MNHN 20369 View Materials ). — KARUBAR: 20375); stn DW 754 , Passe de Dumbéa, 22°23’S, 166°13’E, stn CP 89, Tanimbar Islands, 08°39’S, 131°08’E, 1084- 1058 m, 577-780 m, 1 dd, paratype ( MNHN 20376 View Materials ) GoogleMaps .

2 dd, paratypes ( MNHN 20370) Vanuatu. MUSORSTOM 8: stn DW 1045, 16°54’S, 168°20’E, New Caledonia proper. BIOCAL: stn CP 74, 22°14’S, 167°29’E, 459-488 m, 1 dd, holotype ( MNHN 20367; Figs 55G, H).

1300-1475 m, 1 dd, paratype ( MNHN 20371 View Materials ) . — BATHUS 1 : Fiji. MUSORSTOM 10: stn CP 1354, SE of Viti Levu , 17°43’S, stn CP 671, Passe du Cap Baye, 20°51’S, 165°28’E, 450-470 178°55’E, 959-963 m, 2 dd, paratypes ( MNHN 20377 View Materials ) GoogleMaps .

DISTRIBUTION. — Collected from the Philippines, Indonesia, New Caledonia, Vanuatu and Fiji, (Fig. 58), in 470- 1300 m.

DESCRIPTION. — Shell morphology. Length 6 mm, width 3 mm (holotype). Shell solid, oval-elongate, with nearly parallel sides (Fig. 55G). Only 1 whorl visible, forming nearly the entire shell. Apex and anterior end of the shell rounded. Aperture as long as the shell, wider anteriorly, narrowing abruptly at about 1/4 of the shell length, and ending in a narrow canal. Columellar margin conspicuously thickened. Columella with a conspicuous denticle. Sculpture of a number of fine, irregular, punctuated spiral grooves (Fig. 55H). The punctuations are small and situated next to each other, occasionally fused together forming irregular continuous lines. Colour uniform dirty white.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — Cylichnium nanum is here placed in the genus Cylichnium because of the shape of its shell, which is elongate with a rounded apex and with the aperture ending in a narrow canal. However, only when complete specimens and anatomical information become available will confirmation of this as the correct generic placement be possible.

This species differs from Cylichnium ancillarioides (Schepman, 1913) and C. mucronatum n. sp. in its smaller shell, the presence of a conspicuous tooth on the columella, and the more rounded apex.

Retusa spatha Watson, 1883 from the Caribbean, is the species most similar to C. nanum in shell morphology and future revision will probably transfer it to Cylichnium . Differences between these species include the presence of a single conspicuous tooth on the columella of C. nanum rather than 2 smaller denticles in Retusa spatha .

ETYMOLOGY. — From the Latinization of the Ancient Greek nanos (dwarf), in reference to the small size of this species.