Typhlosyrinx supracostata ( Schepman, 1913 )

Bouchet, P. & Sysoev, A., 2001, Typhlosyrinx - like tropical deep-water turriform gastropods (Mollusca, Gastropoda, Conoidea), Journal of Natural History 35 (11), pp. 1693-1715 : 1699-1701

Typhlosyrinx supracostata ( Schepman, 1913)

(figures 2, 14–22)

Surcula supracostata Schepman, 1913: 422 , pl. 27, figure 8.

Typhlosyrinx supracostata: Powell, 1969: 361 , pl. 272, figures 4–7; Shuto, 1970: 39, pl. 3, figures 9, 10.

NOT Typhlosyrinx supracostata : M atsukuma et al., 1991: pl. 72, figure 7 [= L. matsukumai ].

Type material. Of two syntypes, one ( ZMA 313035 ) is 26.6 mm high, quite worn and with a much damaged aperture, the other ( ZMA 313034 ) measures 31.9 ✕11.3 mm and is in better condition (figures 14, 15); this is the specimen illustrated by Schepman (1913) and Shuto (1970). Because the name Surcula supracostata has been applied by reference to the latter specimen, it is here selected as lectotype.

Type locality. Indonesia, F lores Sea , 07°24'S, 118°15.2'E, 794 m [‘ Siboga ’, sta. 45].

Material examined. Indonesia. Albatross : Sta. 5592, Sibuko Bay, Borneo, S of Silungan I. , 04°12.44'N, 118°27.44'E, 305 fms [558 m], two dd ( USNM 229306 ; USNM 278957 , illustrated by Powell, 1969: pl. 272, figures 6, 7). Sta. 5618, Molucca Passage , 00°37.00'N, 127°15.00'E, 417 fms [763 m], one dd ( USNM 239258 ). Corindon : Sta. CH 240, 00°37'S, 119°37'E, 675 m, one dd. Sta. CH 276, 01°55'S, 119°13'E, 395–450 m, one lv, two dd. Sta CH 280, 01°59'S, 119°10'E, 715–800 m, four lv. K arubar: Sta. CP52, 08°03'S, 131°48'E, 1244–1266 m, two lv. Sta. CP54, 08°21'S, 131°43'E, 836–869 m, 38 lv, six dd (figures 20, 21). Sta. D E55, 08°16'S, 131°47'E, 852-854 m, one lv. Sta. CP73, 08°29'S, 131°33'E, 840–855 m, seven lv, three dd (figures 18, 19). Sta. CP87, 08°47'S, 130°49'E, 1017–1024 m, three lv, three dd. Sta. CP89, 08°39'S, 131°08'E, 1058–1084 m, two lv, one dd. Sta. CP91, 08°44'S, 131°05'E, 884–891 m, eight lv, two dd (figures 16, 17) . Philippines. Musorstom 2: Sta. CP81, 13°34'N, 120°31'E, 856–884 m, eight lv, two dd (figure 22) .

Distribution. Indonesia and the Philippines, alive in 450–1244 m.

Description. Shell broad, thin, spire occupying 38–40% of total shell height. Apex (protoconch and fi rst one to two teleoconch whorls) dissolved in all specimens examined. Teleoconch with up to at least nine whorls, suture shallow, impressed. Whorls weakly convex, subsutural ramp very concave and periphery in lower third on spire whorls, ramp poorly de fi ned and periphery at about mid-whorl height on adult whorls. Axial ribs rather high, weakly nodulose, on early whorls occupying abapical half of whorl, most prominent point in whorl middle. Last two or three adult whorls usually smooth. Spiral cords low, separated by narrow grooves, occupying lower half of whorls with axial ribs, and becoming obsolete together with the ribs. Base and siphonal canal with strong cords but prominence and extension vary between specimens. Based on growth lines, anal sinus deepest at middle of subsutural ramp, broad and shallow. Shells of specimens from depths of 450–700 m are smaller (specimens of 33–37 mm appear to be adult), have a more sturdily built shell and are more distinctly coloured, as is the specimen illustrated by Powell (1969) which has a broad, light salmon-brown band above periphery; those from 800 to 1200 m are larger, up to 57.6 ✕21.5 mm, thinner and brownish yellow.

Radular teeth of medium size, length 290 m m for a specimen with shell height 38.3 mm, with two rather strong barbs at tip of blade, and small basal part with large spur.

Remarks. When he described Surcula supracostata, Schepman (1913) stated that he did not know of any similar species, being apparently unaware of Smith’s (1899) Pleurotoma praecipua . What he considered to be characteristic of S. supracostata , i.e. the difference in sculpture between the early and subsequent whorls, is in fact a generic character of Typhlosyrinx . Powell (1969) treated T. praecipua and T. supracostata as closely allied but distinct species, differing in shell proportions and the presence or absence of spiral cords on the shell base. However, shell proportions are variable and overlap (figures 49, 50) and the development of cords on the shell base is a matter of degree. Our material from Indonesia identi fi able as T. supracostat a differs from Indian Ocean material identi fi able as T. praecipua in the sculpture of the early whorls (figure 51), the ribs being shorter, stronger and more nodulose in the latter. However, because of the lack of geographically intermediate material between southern India ( T. praecipua ) and central/eastern Indonesia ( T. supracostata ), we cannot rule out that these differences relate to mere geographical/populational variants of a single biological species.