Temporal range: 83–0 Ma Campanian to Present
Squalus is a genus of dogfish sharks in the family Squalidae. Commonly known as spurdogs, these sharks are characterized by smooth dorsal fin spines, teeth in upper and lower jaws similar in size, caudal peduncle with lateral keels; upper precaudal pit usually present, and caudal fin without subterminal notch. In spurdogs, the hyomandibula (the bone connecting the braincase to the jaws) is oriented at a right angle to the neurocranium, while in other sharks, the hyomandibula runs more parallel to the body. This led some to think that the upper jaw of Squalus would not be as protractile as the jaws of other sharks. However, a study that compared different jaw suspension types in sharks showed that this is not the case and that Squalus is quite capable of protruding its upper jaw during feeding.
There are currently 30 recognized species in this genus:
- Squalus acanthias Linnaeus, 1758 (Spiny dogfish) 
- Squalus acutipinnis Regan, 1908 (Blunt-nose spiny dogfish) 
- Squalus albicaudus Viana, M. R. de Carvalho & U. L. Gomes, 2016 (Brazilian white-tail dogfish) 
- Squalus albifrons Last, W. T. White & J. D. Stevens, 2007 (Eastern high-fin spurdog)
- Squalus altipinnis Last, W. T. White & J. D. Stevens, 2007 (Western high-fin spurdog)
- Squalus bahiensis Viana, M. R. de Carvalho & U. L. Gomes, 2016 (Northeastern Brazilian dogfish) 
- Squalus blainville (A. Risso, 1827) (Long-nose spurdog)
- Squalus brevirostris S. Tanaka (I), 1917 (Japanese short-nose spurdog)
- Squalus bucephalus Last, Séret & Pogonoski, 2007 (Big-head spurdog)
- Squalus chloroculus Last, W. T. White & Motomura, 2007 (Green-eye spurdog)
- Squalus crassispinus Last, M. J. Edmunds & Yearsley, 2007 (Fat-spine spurdog)
- Squalus cubensis Howell-Rivero, 1936 (Cuban dogfish)
- Squalus edmundsi W. T. White, Last & J. D. Stevens, 2007 (Edmund's spurdog)
- Squalus formosus W. T. White & Iglésias, 2011 (Taiwan spurdog)
- Squalus grahami W. T. White, Last & J. D. Stevens, 2007 (Eastern long-nose spurdog)
- Squalus griffini Phillipps, 1931 (Northern spiny dogfish)
- Squalus hemipinnis W. T. White, Last & Yearsley, 2007 (Indonesian short-snout spurdog)
- Squalus japonicus Ishikawa, 1908 (Japanese spurdog)
- Squalus lalannei Baranes, 2003 (Seychelles spurdog)
- Squalus lobularis Viana, M. R. de Carvalho & U. L. Gomes, 2016 (Atlantic lobe-fin dogfish) 
- Squalus megalops (W. J. Macleay, 1881) (Short-nose spurdog)
- Squalus melanurus Fourmanoir & Rivaton, 1979 (Black-tailed spurdog)
- Squalus mitsukurii D. S. Jordan & Snyder, 1903 (Short-spine spurdog)
- Squalus montalbani Whitley, 1931 (Indonesian green-eye spurdog)
- Squalus nasutus Last, L. J. Marshall & W. T. White, 2007 (Western long-nose spurdog)
- Squalus notocaudatus Last, W. T. White & J. D. Stevens, 2007 (Bar-tail spurdog)
- Squalus quasimodo Viana, M. R. de Carvalho & U. L. Gomes, 2016 (Humpback western dogfish) 
- Squalus rancureli Fourmanoir & Rivaton, 1979 (Cyrano spurdog)
- Squalus raoulensis Duffy & Last, 2007 (Kermadec spiny dogfish)
- Squalus suckleyi (Girard, 1855) (Pacific spiny dogfish)
- Sepkoski, J.J.Jr (2002). "A Compendium of Fossil Marine Animal Genera". Bulletins of American Paleontology, 363: 1-560.
- Wilga, C.D., Motta, P.J. & Sanford, C.P. (2007): Evolution and ecology of feeding in elasmobranchs. Integrative and Comparative Biology, 47 (1): 55-69.
- Viana, S.T.d.F., Carvalho, M.R.d. & Gomes, U.L. (2016): Taxonomy and morphology of species of the genus Squalus Linnaeus, 1758 from the Southwestern Atlantic Ocean (Chondrichthyes: Squaliformes: Squalidae). Zootaxa, 4133 (1): 1-89.
- Viana, S.T.d.F. & Carvalho, M.R.d. (2016): Redescription of Squalus acutipinnis Regan, 1908, a Valid Species of Spiny Dogfish from Southern Africa (Chondrichthyes: Squaliformes: Squalidae). Copeia, 104 (2): 539-553.
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