Admete sadko Gorbunov 1946

Admete sadko Gorbunov, 1946

Admete sadko Gorbunov 1946b: 310, 319, Plate I, fig 5.

Type material: 1 syntype (empty shell), Laptev Sea, 76°12.9’N, 133°50’E, 47 m, R/ V Sadko, 21.08.1937, sta. 21, gray silt with sand (Fig. 1), ZIN 1 /61903. Gorbunov (1946b) also reported one more sample with two syntypes. The sample, however, has not been found during careful examination of ZIN collection and is apparently lost.

Type locality: Laptev Sea, 76°12.9’N, 33°50’E, 47 m and 75°22’N, 135°00’E, 40 m.

Other material: 1 living specimen and 1 empty shell, Kara Sea, 75°45’N, 86°05’E, 29 m, R/V Sadko, 20.08.1936, sta. 3, silt, ZIN 3/ 53455; 1 living specimen, Laptev Sea, 76°09’N, 120°00’E, 64 m, R/ V Sadko, 7.10.1937, sta. 77, ZIN 2 / 62429.

Redescription. Shell of medium size for genus (Table 1), fusiform, fragile (Fig. 1, 2 A–B). Periostracum not marked. Whorls shouldered divided by deep suture. Spiral sculpture consists of prominent cords separarted by spaces of relatively equal size. Body whorl has up to 10 cords: 2—on shoulder of whorl 3–4 on periphery and 2–4 lesser developed cords on base of shell. Surface of cords often covered with secondary spiral riblets. Usually shoulder cords have weak wavy protrusions. Axial sculpture consists only of approximately straight growthlines. Early whorls eroded on all specimens, protoconch unknown. Aperture broad oval, large, its height is about 0.5 of total shell height. Siphonal canal short, slightly bended to the left. Outer lip rounded, corrugated reflecting spiral sculpture. Usually 2 weak collumelar folds present. Umbilicus closed. Operculum absent.

AH—aperture height, AW—aperture width, LWH—last whorl height,

PWH—penultimate whorl height, PWW—penultimate whorl width, SH—shell height, SW—shell width.

Soft parts unknown (studied material contains only subadult living specimens). According to Gorbunov (1946b), radula in Admete sadko is absent.

Distribution. Admete sadko is known from the Laptev and the Kara seas. Reports of the species from the Northern Atlantic (Petit & Harasewych 2005; Hemmen 2007) are erroneous.

Habitat. Found on silty substrates, 29- 64 m.

Etymology. The species is named after R/V Sadko, the ship from which the type samples were collected. Sadko (masculine, singular) is a hero of a Russian folktale. The word “ sadko ” was used as a noun in apposition.

Remarks. Despite the very characteristic shell of Admete sadko, the species had not been recognized since its first description. This is likely due to the unclear first diagnosis and original figures that inaccurately reflect the proportions of shells and sculpture of molluscs described by Gorbunov (1946b). The species is also not very common.

Gorbunov (1946b) gives two accounts of Admete sadko: a description in Russian on page 310 and its English translation on p. 319. Both agree with each other, but the Russian description contained some details that were missing in the English diagnosis. The name Admete sadko is also mentioned in a checklist by Gorbunov 1946a, another paper from the same volume with an original description of the species (Gorbunov 1946b). This publication contains biogeographical and ecological summary of benthos from the Laptev and East Siberian seas, without any comments on species taxonomy and diagnostics, which does not constitute a species description according to article 13.1 of the International Code of the Zoological Nomenclature.

Admete sadko can be recognized from all species of Cancellariidae living in the Arctic by its sculpture of heavy spiral cords (Fig. 2). The species has a broader shell than A. viridula, A. clivicola (Fig. 2G), Admete contabulata (Fig. 2E) and Iphinopsis solida (Fig. 2F). These three latter species are also considerably smaller than Admete sadko. Admete sadko also differs from Iphinopsis inflata by the absence of an umbilicus. Admete solida have a similar shell proportions but can be recognized by its low spiral sculpture and rounded whorls (Sysoev & Kantor, 2002; Kantor & Harasewych, 2003).