Squalus

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 : 83

Key to species of Squalus from the Southwestern Atlantic Ocean

1a. First dorsal spine placed well behind vertical line traced at adpressed pectoral free rear tips; white spots dorsally on body; unilobed anterior margin of nostrils; pectoral girdle with anterolateral segmented processes................... S. acanthias .

1b. First dorsal spine placed over or before vertical line traced at adpressed pectoral rear tips; body uniformly colored dorsally; bilobed anterior margin of nostrils; pectoral girdle without any segmented processes............................... 2.

2a. Prenarial length smaller than distance between nostril and upper labial furrow; upper caudal lobe very narrow; pectoral fins very narrow with pectoral free rear tips pointed and angular; caudal fin mostly white; dermal denticles unicuspid and lanceolate; dorsal terminal cartilage (claw) short, thick and straight at tip; accessory terminal cartilage (spur) broad and small.............................................................................................. S. albicaudus .

2b. Prenarial length greater than distance between nostril and upper labial furrow; upper caudal lobe broad and rectangular; pectoral fins broad with pectoral free rear tips rounded and lobe-like; caudal fin grayish; dermal denticles tricuspid and rhomboid; dorsal terminal cartilage (claw) very elongate, slender and hook-like at tip; accessory terminal cartilage (spur) thin and large.................................................................................................... 3.

3a. Body robust and markedly humped dorsally; first dorsal fin conspicuously slender only from its midline to apex; second dorsal fin upright and markedly tall (height 4.0%–5.3% TL); dermal denticles markedly imbricate and broad at crown...................................................................................................... S. quasimodo .

3b. Body very slender throughout, without a dorsal hump; first dorsal fin uniformly slender; second dorsal fin raked and low (height 3.7%–4.4% TL); dermal denticles not imbricate and very narrow.......................................... 4

4a. First and second dorsal fins very broad; caudal fin dark gray with dorsal caudal margin light gray and ventral caudal lobe uniformly dark gray; interdorsal space 21.9%–24.1% TL; dorsal caudal space 10.4%–10.9% TL; pectoral-caudal space 20.3%– 24.4% TL in adults; pectoral inner margin 9.2%–10.6% TL........................................... S. lobularis .

4b. First and second dorsal fins narrow; caudal fin light gray with dorsal caudal margin white and ventral caudal lobe mostly white; interdorsal space (24.4%–26.8% TL); dorsal-caudal space 11.0%–12.2% TL; pectoral-caudal space 19.5%–20.3% TL; pectoral inner margin 8.4%–8.9% TL........................................................... S. bahiensis .