Cylichnium ancillarioides (Schepman, 1913)

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 699-703

Cylichnium ancillarioides (Schepman, 1913)

Figs 55A, B, E, 56A-C, 57A, 58

Volvulopsis ancillarioides Schepman, 1913: 463 , pl. 31, fig. 4.

Synonyms:

Cylichnium matsumotoi Habe, 1955: 73 .

Cylichnium sumatrense Thiele, 1925: 267-268 , pl. 31, figs 7, 7a.

TYPE MATERIAL. — V. ancillarioides : holotype ZMA 3.13 .108 . — C. matsumotoi : holotype NSMT Mo 38563 . — C. sumatrense : 11 syntypes MNHB .

TYPE LOCALITY. — V. ancillarioides: Savu Sea , Indonesia, 9°03.4’S, 119°56.7’E, 959 m [ Siboga : stn 052]. — C. matsumotoi : Kumano-nada off Owase, eastern Kii Peninsula, Japan, 120 m — C. sumatrense: Siberut Island, Indonesia, 0°39.2’S, 98°52.5’E, 750 m [ Valdivia : stn 191].

MATERIAL EXAMINED. — Philippines. MUSORSTOM 2: stn 936 m, 1 dd; stn DW 1011 , 17°50’S, 168°12’E, 547-585 m, 1 dd; CP 79, 13°44’N, 120°32’E, 682-770 m, 1 dd . — ESTASE 2: CP 2, stn CP 1055, 16°30’S, 167°55’E, 572-580 m, 1 lv, dissected (Figs 14°05’N, 120°02’E, 2050 m, 1 dd. 56A-C, 57A).

Indonesia. The type material of C. sumatrense . — KARUBAR: stn Fiji. MUSORSTOM 10: stn CP 1353, SE of Viti Levu, 17°31’S, CP 91, Tanimbar Islands , 08°44’S, 131°05’E, 884-891 m, 2 dd. 178°53’E, 879-897 m, 6 dd; stn CP 1354, 17°43’S, 178°55’E, Coral Sea. MUSORSTOM 5: stn 321, 21°20’S, 158°02’E, 1000 959-963 m, 1 dd; stn CP 1361, 18°00’S, 178°54’E, 1058-1091 m, m, 1 dd (Fig. 55E). 1 dd . — BORDAU 1 : stn CP 1392, 16°49’S, 179°54’E, 545-651 m , New Caledonia proper. BATHUS 2 : stn CP 743, Passe de Boul- 1 dd (Figs 55A, B); stn CP 1392, 16°49’S, 179°54’E, 545-651 m, ari, 22°36’S, 166°26’E, 713-950 m, 4 dd. 6 dd (1, LACM 153247 ); stn CP 1395, 16°45’S, 179°59’E, 423 -

Loyalty Ridge. BIOGEOCAL: stn CP 238, 21°28’S, 166°23’E, 500 m, 1 dd; stn CP 1396, 16°39’S, 179°57’E, 591-596 m, 2 dd; 1260-1300 m, 1 dd; stn CP 243, 21°27’S, 166°26’E, 1820 m, 1 stn CP 1398, 16°22’S, 179°56’E, 907-912 m, 1 dd, stn CP 1400, dd; stn CP 250, 21°25’S, 166°28’E, 2350 m, 1 dd; stn CP 272, 16°28’S, 179°50’W, 1004-1012 m, 23 dd; stn CP 1401, 16°35’S, 21°00’S, 166°57’E, 1615-1710 m, 1 dd. 179°41’W, 600-648 m, 2 dd; stn CP 1407, 16°40’S, 179°39’E,

Vanuatu. MUSORSTOM 8: stn DW 991, 18°51’S, 168°52’E, 910- 499-527 m, 5 dd.

DISTRIBUTION. — Originally described from the Savu Sea and the Makkassar Strait , Indonesia, in 959-1301 m. Subsequently reported from Indonesia, in 614-750 m (Thiele 1925), and off Owase and Chosi , Honshu , Japan, in 120 m (Habe 1955). Material herein collected in the Philippines, Indonesia, Coral Sea, New Caledonia, Vanuatu and Fiji, (Fig. 58), in 500-2350 m, live in 572-580 m.

DESCRIPTION. — Shell morphology. Length 31 mm, width 14 mm (largest specimen examined). Shell solid, oval-elongate, with nearly parallel sides (Fig. 55A). Only 1 whorl visible, forming nearly the entire shell, except for a visible portion of the top of the spire of one specimen, which is encircled by a sharp margin enclosing a small hole (Fig. 55B). Apex rounded or slightly pointed, forming a short cone. Anterior end of the shell rounded. Aperture as long as the shell, wider anteriorly and constricted posteriorly, ending in a narrow canal. Columellar margin conspicuously thickened. Columella twisted near the anterior end of the shell. Juvenile shells shorter, with the aperture about 2/3 of the shell length and a pointed apex (Fig. 55E). Sculpture of a number of fine, irregular spiral lines. Colour uniform dark brown.

Anatomy. The digestive system contains 3 smooth and oval gizzard plates, all of them similar in size and shape (Fig. 56A). The radular formula is 23 x 10.0. 10 in a specimen from Vanuatu (MUSORSTOM 8 stn CP 1055). The lateral teeth are hamate and smooth, with no denticles (Fig. 56C). All teeth are similar in shape and size.

The reproductive system is monaulic (Fig. 57A). The ampulla is long and convoluted. It connects to the narrow and elongate post-ampullary duct. The seminal receptacle enters the post-ampullary duct, which continues distally to the common general atrium. Also entering the common atrium are the female glands and the bursa copulatrix. From the gonopore an open seminal groove runs anteriorly to the protrusible cephalic penis and the prostate. At the vaginal opening there is a complex female copulatory organ (Fig. 56B).

REMARKS. — Schepman (1913) described Volvulopsis ancillarioides based on 2 specimens, collected from the Savu Sea and Makkassar Strait, Indonesia. Subsequently Habe (1955) transferred this species to the genus Cylichnium . Comparison with Schepman’s (1913) illustration of the shell of C. ancillarioides and re-examination of the remaining syntype of this species confirmed that the material here examined from the Coral Sea, Fiji, Indonesia, New Caledonia, the Philippines and Vanuatu belongs to the same species.

Thiele (1925) described Cylichnium sumatrense from Sumatra, Indonesia. The shell of this species is very similar to those of the specimens of C. ancillarioides from Indonesia here examined, and the species are regarded as synonyms.

FIG. 55. Shell morphology of species of Cylichnium Dall,1908 . A, Cylichnium ancillarioides (Schepman,1913) ,(29 mm),ventral view, Fiji, BORDAU 1 stn CP 1392; B, same shell,posterior view. C, Cylichnium mucronatum n. sp., holotype MNHN 20363 (29 mm), ventral view, BORDAU 1 stn CP 1392; D, same shell,posterior view. E, Cylichnium ancillarioides (Schepman,1913) ,juvenile shell (11 mm),ventral view, Coral Sea,MUSORSTOM 5 stn 321. F, Cylichnium mucronatum n. sp., paratype (11 mm), ventral view,Coral Sea,CORAIL 2 stn DW 172. G, Cylichnium nanum n. sp., holotype MNHN 20367 (6 mm), ventral view, MUSORSTOM 8 stn DW 1045; H, same shell, posterior view. FIG. 56. Anatomy of of species of Cylichnium Dall, 1908 . A, Cylichnium ancillarioides (Schepman, 1913) , gizzard plate, Vanuatu, MUSORSTOM 8 stn CP 1055, scale bar = 1 mm; B, same specimen, female copulatory organ, scale bar = 1 mm; C, same specimen, radula, scale bar = 100 Μm. D, Cylichnium mucronatum n. sp., radula of paratype, Fiji, BORDAU 1 stn CP 1400, scale bar = 100 Μm; E, same specimen, female copulatory organ, scale bar = 1 mm; F, same specimen, gizzard plate, scale bar = 2 mm.

Cylichnium matsumotoi was described by Habe (1955) as different from C. ancillarioides based on its having a more cylindrical shell, an entirely concealed spire and a longer columellar margin. However, the holotype of C. matsumotoi , illustrated by Higo et al. (2001), is very similar to the specimens here examined. Thus, C. matsumotoi is here regarded as a synonym of C. ancillarioides .