Acteon aphyodes, 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 : 626-627

“ Acteon ” aphyodes n. sp.

Figs 17F, 19B, C, 21

TYPE MATERIAL. — Holotype MNHN 20272 and 19 paratypes MNHN 20273-20278, 1 paratype LACM 2984 .

TYPE LOCALITY . — Fiji, 18°47’S, 178°47’W, 750-767 m [ BORDAU 1 : stn CP 1460] .

MATERIAL EXAMINED. — Coral Sea. MUSORSTOM 5: stn 321, 775 m, 10 dd, paratypes (MNHN 20276); stn CP 1080, 15°57’S, 21°20’S, 158°02’E, 1000 m, 3 dd, paratypes (MNHN 20273). 167°28’E, 799-850 m, 1 dd, paratype (MNHN 20277) .

Norfolk Ridge. BIOCAL: stn DW 70, 23°25’S, 167°53’E, 965 m, Fiji. BORDAU 1: stn CP 1460, 18°47’S, 178°47’W, 750-767 m, 1 3 dd, paratypes ( MNHN 20274; Figs 17F, 19C). dd, holotype ( MNHN 20272; Fig. 19B).

Loyalty Ridge. BIOGEOCAL: stn DW 289, 20°36’S, 167°00’E, Tonga. BORDAU 2: stn DW 1531, Eua, 21°12’S, 174°56’W, 970-983 830-840 m, 1 dd, paratype (MNHN 20275). m, 1 dd, paratype (LACM 2984); stn DW 1565, NW of Tongatapu,

Vanuatu. MUSORSTOM 8: stn CP 992, 18°52’S, 168°55’E, 748- 20°58’S, 175°16’W, 869-880 m, 1 dd, paratype ( MNHN 20278).

DISTRIBUTION. — The Coral Sea, New Caledonia, Vanuatu, Fiji and Tonga (Fig. 21), in 767-1000 m.

DESCRIPTION. — Shell morphology. Length 15 mm, width 10 mm (holotype). Shell thin, oval, with convex sides (Fig. 19B). Body whorl very large, about 3/4 of the shell length. Spire short, conical, with 3-4 whorls. Suture channeled. Protoconch globose, about 1.5 whorls and 600 Μm in diameter (Fig. 19C). Umbilicus deep and narrow, partially covered by an extension of the columella. Aperture short and wide, wider anteriorly. Aperture about 4/5 of the body whorl length. Anterior end of the aperture expanded into a short lip. Columellar margin thickened, oblique, with a small, single fold. Sculpture of a number of punctuated spiral grooves (Fig. 17F). The punctuations are very large, rounded to oval, partially fused together within each groove. The grooves are separated by thin gaps that are several times narrower than the grooves. Colour uniformly cream.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — “ Acteon ” aphyodes is similar in shell morphology to Punctacteon teramachii (Habe, 1950) , recently redescribed by Hori (2000a). However, these two species are easily distinguishable by the shorter columella of “ A. ” aphyodes with a smaller denticle than that of P. teramachii . Another difference is the morphology of the sculpture, which is composed of spiral grooves separated by thin gaps narrower than the grooves in “ A. ” aphyodes , whereas in P. teramachii the gaps are much wider than the grooves.

Maxacteon milleri Rudman, 1971 also has an oval shell but the spire is shorter than that of “ A. ” aphyodes and the shell is pigmented with orange-brown axial markings (Rudman 1971c), whereas the shell of A. aphyodes is uniformly whitish.

The species with a shell morphology most similar to “ A. ” aphyodes is “ Acteon ” perforatus Dall, 1881, originally described from the Gulf of Mexico in 1470 m. Differences between these two species include the presence of a yellowish band on the suture and smaller punctuations on the spiral grooves of “ A. ” perforatus Dall 1881.

A generic placement for this species is not possible until complete specimens become available for study.

ETYMOLOGY. — From the Ancient Greek aphyoides (whitish), in reference to the colour of the shell.