Somniosus microcephalus

Author: (Bloch and Schneider, 1801)

Somniosus microcephalus (Bloch and Schneider, 1801)

Status in World Register of Marine Species:
Accepted name: Somniosus microcephalus (Bloch and Schneider, 1801) (updated 2009-06-25)

Diagnosis: largest shark of the family. Snout thick, broadly rounded, more tapering before nostrils, snout tip narrowly rounded, length approximately equal to mouth breadth. Nostrils near snout tip, anterior flaps poorly developed. Eye small, circular, over front of mouth. Mouth slightly arched, labial furrows extending back for distance of half mouth width. Upper teeth lanceolate, slightly oblique; lower teeth on broad quadrate base, cusps strongly oblique, forming single cutting edge. Spiracle slightly above and behind eye by distance of 1.5 times eye diameter. Gill openings small, sub-equal in size. Pectoral fins relatively small; first dorsal fin small, brush-shaped; second dorsal fin origin over insertion of pelvic fins, free tip produced, fin height approximately half length of base; distance from free tip of second dorsal to origin of caudal fin approximately equal to second dorsal fin base; upper caudal fin short, pointed, with well-developed sub-terminal notch, lower lobe well developed. Body without lateral luminescent pores. Colour: black or brown to grey. Size: to 6.5 m, common 4.5 m.

Habitat: usually benthic at 200-600 m, but occurring on surface and in coastal waters; very sluggish, passive. Food: omnivorous; various fishes, seals, birds, carrion. Reproduction: oviparous, or ovoviviparous, large numbers of eggs found in females.

Distribution: off Greenland, Iceland and Bear I., in White Sea and, North Sea; possibly also off Portugal. Elsewhere, in north-west Atlantic, from Greenland to Gulf of Maine.

Complementary iconography. Rasmussen and Dannevig, 1960: 75-76, pl. 191 Muus and Dahlström, 1965: 48, fig. 14.
Eggs, embryonic and young stages. Bjerkan and Koefoed, 1957: 1-12, fig. 1-5.