Somniosus rostratus

(Risso, 1827)

Little sleeper shark
Classification: Elasmobranchii Squaliformes Somniosidae

Reference of the original description
Risso, A. (1827)
Histoire naturelle des principales productions de l'Europe méridionale et particulièrement de celles des environs de Nice et des Alpes-maritimes. F.G Levrault, Paris. Vol. 3, 480 pp

Synonyms / new combinations and misspellings
Delatias (Somniosus) rostratus, Laemargus rostratus, Rhinoscymnus rostratus, Scymnus rostratus, Scymnus (Laemargus) rostratus, Somniosus bauchotae, Somniosus cf. rostratus, Somniosus (Rhinoscymnus) cf. rostratus, Somniosus (Rhinoscymnus) rostratus

Somniosus rostratus
XXXX: No types known;
Somniosus bauchotae
Holotype: MNHN: 1976-0012;

Description :

Citation: Somniosus rostratus (Risso, 1827): In: Database of modern sharks, rays and chimaeras,, World Wide Web electronic publication, Version 07/2024

Please send your images of "Somniosus rostratus" to

Somniosus rostratus (Risso, 1827), adult, female, 90.4 cm total length (TL) © L'Elasmogrup, University of Valencia)
Common names
spa Tiburón boreal, spa Tollo boreal, fra \(T\) Laimargue de la Méditerranée, eng Little Sleeper Shark, ita Lemargo

Short Description
Snout short and broadly rounded. Head short, length from snout to pectoral fins 20 to 23% TL in specimens above 70 cm TL. Cusps of most lower teeth large, high, and semioblique, roots low. Total tooth rows upper jaw 53 and for lower jaw 31 to 36. Lateral trunk denticles with flat, wide, crowns and horizontal cusps, giving skin a smooth texture. Insertion of first dorsal fin closer to pectoral–fin bases than pelvic–fin bases. Interdorsal space equal or greater than distance from snout tip to second gill slits. A short lateral keel present on base of caudal fin. Caudal peduncle short, distance from second dorsal–fin insertion to upper caudal– fin origin 2 times second dorsal–fin base or less, distance from pelvic–fin insertions to lower caudal–fin origin subequal to dorsal caudal–fin margin. Vertebral column with well–defined centra. Vertebral counts: total vertebral count 78, precaudal vertebral count 58. Spiral valve turns: 23. Size small, not exceeding 140 cm. Colour: uniformly blackish without transverse dark bands, small light spots, and blotches. [17836].

Northeast Atlantic: Madeira, France, and western Mediterranean. Western Pacific: off New Zealand [1388] and Japan. Source:

Human uses
fisheries: minor commercial; price category: not marketed/unknown; price reliability:

Ovoviviparous [518]. Young born at 21-28 cm [578]. Distinct pairing with embrace [17086].

Size / Weight / Age
143 cm TL (male/unsexed; [578])

bathydemersal; marine; depth range 200 - 1000 m [518]

tooth formula (upper/lower): 30/16-18 [1131];

Links: SEM-images of teeth

shark-references Species-ID=6499;

Parasites (arranged by Jürgen Pollerspöck)
  • Acanthobothrium coronatum (Rudolphi, 1819) Van Beneden, 1850 [16448]
  • Sphyriocephalus viridis (Wagener, 1854) Pintner, 1913 [16112]