Squalus Linnaeus, 1758

De, Sarah T., De, Marcelo R. & Gomes, Ulisses L., 2016, Taxonomy and morphology of species of the genus Squalus Linnaeus, 1758 from the Southwestern Atlantic Ocean (Chondrichthyes: Squaliformes: Squalidae), Zootaxa 4133 (1), pp. 1-89 : 7-8

Genus Squalus Linnaeus, 1758

Squalus Artedi, 1738: 504 (description); Linnaeus, 1758: 233 (original description; “Oceano Europaeo”); Molina, 1782: 188, 189 (listed; Chile); Rafinesque, 1810: 45 (listed; Sicily); Girard, 1855 (listed; Chile); Gill, 1862: 367–405 (in classification); Poey, 1868: 211, 213, 454 (listed; Cuba); Berg, 1895: 5, 6 (listed; Argentina and Uruguay); Jordan & Evermann, 1898: 53, fig. 24 (listed; North and Central America); Schreiner & Ribeiro, 1903: 79 (listed; Brazil); Jordan, 1907: 202 (cited); Miranda Ribeiro, 1907: 167, 168 (listed; Brazil); Regan, 1908: 39, 45, 48 (identification key, listed; global); Garman, 1913: 191 (description; global); Miranda Ribeiro, 1923 (listed; Brazil); Howell-Rivero, 1936: 45 (revision; Cuba); Fowler, 1936: 69–71 (description; Western Africa); Fowler, 1941: 129 (listed; Brazil); Bigelow & Schroeder, 1948: 451–480, figs 87–90 (revision; Northwestern Atlantic); Bigelow, Schroeder & Springer, 1953: 220–222 (cited; Western Atlantic); Bigelow & Schroeder, 1957: 26–37, figs 3, 4 (description); Ledoux, 1970, 65–69 (revision; Mediterranean Sea); Bass et al., 1976 (revision; Eastern South Africa); Figueiredo, 1977: 8 (listed; Southeastern Brazil); Cadenat & Blache, 1981: 46–52; figs 28–31 (revision; Mediterranean Sea, North Atlantic Ocean); Figueiredo, 1981: 17 (listed; Brazil); Lucena & Lucena, 1981: 2–4 (listed; Brazil); Compagno, 1984: 109–123 (revision; global); Kondyurin & Myagkov, 1984: 118–120, (revision; Western Atlantic); Menni et al., 1984: 62, 83, 84 (listed; Argentina and Uruguay); Myagkov & Kondyurin, 1986: 1–20 (revision; Atlantic); Muñoz-Chápuli & Ramos, 1989 (revision; Eastern Atlantic); Gadig & Moreira, 1992: 112, 118 (cited; Brazil); Calderón, 1994 (cited; Brazil); Marques, 1994 (description; Brazil); Gomes et al., 1997: 93–98 (listed, description; Brazil); Cervigón & Alcal, 1999: 122 (revision; Venezuela); Compagno & Niem, 1999: 1229–1232 (revision; Western-Central Pacific); Lessa et al., 1999 (cited, listed; Brazil); Marques, 1999 (description; Brazil); Mazzoleni & Schwingel, 1999: 114 (listed; South Brazil); Gadig et al., 2000: 129 (cited; Cear, Brazil); Gadig, 2001: 54–59 (revision; Brazil); Soto, 2001: 94–96 (listed; Brazil); Compagno, 2002: 380–385 (revision; Western Central Atlantic); Nion et al., 2002: 4, 65 (listed; Uruguay); Haimovici et al., 2003 (cited; Brazil); Meneses & Paesch, 2003: 7, 8, 25 (listed; Uruguay, Argentina); Heemstra & Heemstra, 2004 (cited, Southern Africa): 49, 53–54; Soto & Mincarone, 2004: 73–82 (listed; Brazil); Compagno et al., 2005: 72 (description; global); Haddad & Gadig, 2005 (cited; Brazil); Lamilla & Bustamante, 2005: 9, 26 (cited; Chile); Hazin et al., 2006 (cited; Northeastern Brazil); Jablonski et al., 2006 (cited; Brazil); Nelson, 2006: 66 (listed; global); Last et al., 2007 (revision; Australia); Louro & Rossi- Wongtschowski, 2007 (cited; Brazil); Menni & Lucifora, 2007: 2, 3 (listed; Argentina, Uruguay); Pon & Gandini, 2007 (cited; Argentina); Carrier et al., 2010: 44, 127, 139 (cited); Gomes et al., 2010: 44, 45 (cited; Brazil); Menni et al., 2010 (cited; Southwestern Atlantic); Saéz et al., 2010: 623, 624 (identification key; Chile); Tomás et al., 2010 (cited; Brazil); Viana, 2011: 1–373 (description; Southwestern Atlantic); Eschmeyer & Fricke, 2015 (listed; global); Bornatowski & Abilhoa, 2012: 35 (cited; Brazil); Rosa & Gadig, 2014: 92, 97 (listed, cited; Brazil).

Acanthorhinus Blainville, 1816: 121 (original description, not illustrated); Fowler, 1936: 61 (cited); Bigelow & Schroeder, 1948: 452 (cited).

Spinax: Cuvier, 1817: 130 (cited); Cuvier, 1863: 320 (listed).

Acanthias Risso, 1826: 131 (original description, not illustrated; Mediterranean Sea); Müller & Henle, 1841: 83 (listed); Gill, 1861: 60 (listed; North and Central America; used Squalus for Carcharhinus in this work); Duméril, 1865: 435, 436 (description); Günther, 1866: 384, 396 (listed; Central America); Vaillant, 1888: 7 (cited; Argentina).

Type species: Squalus acanthias Linnaeus, 1758 by subsequent designation of Gill (1862: 405).

Diagnosis. Squalus is characterized by the following combination of characters: slender and fusiform body, arched dorsally at anterior region; lateral keels restricted to caudal peduncle; short snout, rounded or obtuse at the tip; anterior nasal flaps lobe-like, however without forming nasal barbels; presence of slender dorsal spines without lateral grooves prior to each dorsal fin, extending or not to the apex of corresponding fin; second dorsal fin considerably smaller and more raked than first dorsal fin; caudal peduncle with conspicuous upper and lower precaudal pits; asymmetric caudal fin without subterminal notch; dorsal caudal lobe considerably greater in length than ventral caudal lobe; teeth unicuspid, small, similar in both jaws with short, slightly oblique cusps; dermal denticles unicuspid or tricuspid.

Squalus is distinguished from Cirrhigaleus in having anterior nasal flaps with short secondary lobe without forming nasal barbels ( vs. secondary lobe very elongated and forming nasal barbels extending to anterior margin of mouth), second dorsal fin smaller and lower than first dorsal fin ( vs. dorsal fins of similar length and height with second dorsal fin as high and large as first dorsal fin), second dorsal-fin spine larger in length than first dorsal-fin spine ( vs. second dorsal-fin spine equal in length to first dorsal-fin spine), and conspicuous upper and lower precaudal pits ( vs. absence of lower precaudal pit). It is further differentiated from Cirrhigaleus by having narrow dermal denticles ( vs. denticles conspicuously broad), and body fusiform and somewhat arched dorsally throughout all of its length ( vs. body robust and markedly humped dorsally).