Somniosus pacificus

Bigelow & Schroeder, 1944

Pacific sleeper shark
Classification: Elasmobranchii Squaliformes Somniosidae

Reference of the original description
Bigelow, H.B. & Schroeder, W.C. (1944)
New sharks from the Western North Atlantic. Proceedings of the New England Zoölogical Club, 23, 21–36

Synonyms / new combinations and misspellings
Somniosus cf. pacificus, Somniosus (Somniosus) pacificus

Somniosus pacificus
Holotype: MCZ: 1103-S

Description :

Citation: Somniosus pacificus Bigelow & Schroeder, 1944: In: Database of modern sharks, rays and chimaeras,, World Wide Web electronic publication, Version 07/2024

Please send your images of "Somniosus pacificus" to

Somniosus pacificus Bigelow & Schroeder, 1944, TL 286 mm, coll.: Pacific Shark Research Center, MLML; © Digital Fish Library
Common names
spa Tiburón dormilón del Pacifico, spa Tollo dormilón, spa Tollo negro dormilón, fra \(T\) Laimargue dormeur, eng Pacific sleeper shark, eng Sleeper shark, eng Southern sleeper shark

Short Description
Uniformly greyish-pink with bluish black fins; live specimens probably with white spots on dorsal surface [1388]. Short rounded snout, heavily cylindrical body and small precaudal fins, equal-sized dorsal fins, asymmetrical caudal fin with a well-developed ventral lobe [1388], first dorsal fin on back closer to pelvic fins than pectoral fins, interdorsal space less than distance from snout tip to first gill openings, no short keels on base of caudal fin, upper teeth lanceolate, lower teeth with short, low, strongly oblique cusps and high narrow roots [518]. Diet: Gulf of Alaska (data base: 13 stomachs were analyzed): Arrowtooth flounder, Atheresthes stomias, was the most important prey, representing 67% of the total stomach content weight (64% of frequency of occurrence). Other prey included a 48-cm walleye pollock, Theragra chalcogramma (5.2% by weight), a single 33-cm rockfish, Sebastes sp., a 40-cm Pacific salmon, Oncorhynchus sp., and a 26-cm flathead sole, Hippoglossoides elassodon, as well as three unidentifiable flatfish. Octopus dofleini were the most important invertebrate found in the diet of sleeper sharks, representing 5% of the total stomach contents weight and 73% of the frequency of occurrence. Less important invertebrate prey included squids, snails (Fusitriton sp.), hermit crabs, and gammarid amphipods. [16996].

North Pacific: Japan and along the Siberian coast to the Bering Sea, southern California (USA), and Baja California, Mexico. Sporadic records from the South Pacific (assignment of large southern hemisphere Somniosus to the North Pacific Somniosus pacificus is tentative) [544]. In Australasian waters, it occurs from the seamounts south of Tasmania, the Challenger Plateau (off eastern New Zealand) and possibly from Macquarie Island [1388]. Southwest Atlantic: off Uruguay [3717], Brazil (Ref. 53443) and Argentina [5839]. Source:

Human uses
fisheries: of no interest

Probably ovoviviparous [518]. Size at birth 42 cm or less [578]. Distinct pairing with embrace [17086]. Found on the continental slope (Ref. 75154).

Size / Weight / Age
440 cm TL (male/unsexed; [518]); 430 cm TL (female)

benthopelagic; marine; depth range 0 - 2000 m [578]

shark-references Species-ID=6498;

Parasites (arranged by Jürgen Pollerspöck)
  • Erpocotyle somniosi (Causey, 1926) Price, 1942 [17919]