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Comprehensive Description

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Description

Dentalium majorinum MABILLE & ROCHEBRUNE, 1889

 

(Figs 3, 8, 10)

 

 

Dentalium majorinum MABILLE & ROCHEBRUNE, 1889 in ROCHEBRUNE & MABILLE 1889: H100, pl. 4 fig. 10; PILSBRY & SHARP 1897-98: 27, pl. 12 figs 98-99; PLATE 1908a: 1; SMITH 1915: 74; HEDLEY 1916: 67, pl. 9 figs 104, 105; CARCELLES 1950: 72, pl. 3 fig. 61; CARCELLES & WILLIAMSON 1951: 321; CASTELLANOS 1979: 133; VOSS 1988: 42, figs 4-18; DI GERONIMO et al. 1992: 207.

 

Dentalium majorinum var. magellanicum PILSBRY & SHARP, 1897-98: 27, 28, pl. 12 figs 95-97.

 

Dentalium shoplandi, – MELVILL & STANDEN 1907: 143 (non JOUSSEAUME, 1894).

 

Dentalium majorinum gaussianus PLATE, 1908b: 5; POWELL 1960: 169.

 

Dentalium sp. cf. shoplandi, – LAMY 1910: 324, 1911: 16 (non JOUSSEAUME, 1894). Dentalium majorinum var. grahamense ODHNER, 1931: 4, pl. 1 fig. 4.

 

Dentalium sp. (cf. skoplandi) (sic), — CARCELLES 1953: 206 (non JOUSSEAUME, 1894).

 

Dentalium majorinum grahamense, – CARCELLES 1953: 206, pl. 4 fig. 88; POWELL 1960: 169.

 

Dentalium (Fissidentalium) magellanicum, – POWELL 1958: 207.

 

Dentalium magellanicum POWELL, 1960: 169; ARNAUD 1965: 212.

 

Dentalium (Fissidentalium) majorinum, – DELL 1964: 123; ARNAUD 1974a: 554; 1974b: 644.

 

Fissidentalium (Fissidentalium) majorinum, – SCARABINO 1979: 60, figs 64, 91.

 

Fissidentalium majorinum, – DELL 1990: 72.

 

 

Type material. – Syntypes of D. majorinum MNHN; lectotype of D. m. gaussianum ZMB 59730a (designated by KILIAS 1995: 175), paralectotype ZMB 59730b; syntypes of D. m. magellanicus USNM 87561, USNM 601272; syntypes of D. m. var. grahamense SMNH 4193.

 

Type locality. – Baie Orange, Chile (near Cape Horn).

 

Present material. – 38-1140: 1 L, 37-1246: 14 L (predominantly juvenile), 36-1124: 5 L, 33-1077: 2 L, 32-1045: 13 L, 31-1263: 97 mostly L, 29-1270: 1 D (juvenile shell with bore hole), 28-1279: 3 L.

 

 

Description. – Shell: up to 34.7 mm long, slender, slightly to moderately curved, slowly expanding; white, larger shells frequently with brownish or black incrustations in the posterior half; sculpture of 10 to 14 primary ribs increasing to up to 28 towards the aperture by intercalation (longest specimen without intercalation: 20.5 mm, shortest specimen showing intercalation: 8.7 mm); intercostal spaces concave, usually all ribs reach the aperture except for large specimens where the youngest part of the shell may be sculptured by growth lines only; cross section polygonal or circular; apex entire or with shallow ventral notch, but no slit; larval shell (in one specimen) typical for the Dentaliida (STEINER 1995) with six annular swellings, earliest juvenile shell sculptured by growth lines only.

 

Radula: typical for the genus with evenly curved, hoof-shaped rhachis tooth, lateral teeth well developed head bearing four cusps, the posterior one being slightly prominent, marginal teeth sigmoidal.

 

 

Remarks. – The largest specimen reported is 57 mm long (PILSBRY & SHARP 1897-98). The variation in number of primary and intercalating ribs as well as in the distance between the apex and the onset of intercalation within this single population supports the opinion of DELL (1964) that the differentiation of varieties or subspecies is not appropriate.

 

 

Distribution. – Circumantarctic: Cape Horn region, Southeast Pacific south of 46ºS, Atlantic south of 35°S, Falkland Islands, South Shetland Islands, Weddell Sea, Palmer Archipelago, Bellinghausen Sea, Ross Sea, off the Antarctic coast from 49°E to 169ºE. 68-1247 m.”

 

 

(Steiner & Linse, 2000: 17-18)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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