Field Key to Sharks Encountered in the U.S. Atlantic Bottom Longline Shark Fishery and by Recreational Anglers © George Burgess, Florida Program for Shark Research

1a) Body flattened dorso-ventrally, skate-like in appearance ................................................................. Squatina dumeril - Atlantic angel shark

1b) Body round in cross section.......................................................................................... 2

2a) Seven gill slits, single dorsal fin.................. Heptranchias perlo - sharpnose sevengill shark

2b) Six gill openings, single dorsal fin................................................................................ 3

2c) Five gill openings, two dorsal fins................................................................................ 4

3a) Snout short, blunt and broad; eye small; distance between rear base of dorsal fin and origin of caudal fun about 1.5 to 2.0 times length of dorsal fin base; lower jaw with six rows of teeth...................................................................... Hexanchus griseus, bluntnose sixgill shark

3b) Snout more pointed and narrow; eye large; distance between rear base of dorsal fin and origin of caudal fin about 2.5 to 3 times length of dorsal fin base; lower jaw with five rows of teeth....................................................................... Hexanchus nakamurai, bigeye sixgill shark

4a) Anal fin absent............................................................................................................. 5

4b) Anal fin present............................................................................................................ 9

5a) No spines on dorsal fins............................................. Echinorhinus brucus - bramble shark

5b) Both dorsal fins with spines.......................................................................................... 6

6a) First dorsal spine over or posterior to inner corner of pectoral fin; midpoint of base of pelvic fin much nearer to origin of second dorsal fin than to rear base of first dorsal fin......... 7

6b) First dorsal spine almost over midpoint of inner margin of pectoral fin; midpoint of base of pelvic fin about midway between rear base of first dorsal fin and origin of second dorsal fin.. 8

7a) First dorsal fin noticeably larger than second dorsal fin; anterior nasal flap with small and narrow secondary lobe; usually conspicuous white spots present on sides of body ................................................................................... Squalus acanthias - spiny dogfish

7b) Second dorsal fin nearly as large as first dorsal fin; anterior nasal flap with large and broad secondary lobe, almost barbel-like; color dark without conspicuous white spots on sides of body......................................................................... Cirrhigaleus asper - roughskin dogfish

8a) Inner margins of pectoral fins deeply concave, inner corners acutely pointed................................................................................ Squalus cubensis - Cuban dogfish

8b) Inner margins of pectoral fins weakly concave, inner corners at approximately right angles............................................................................ Squalus blainville - longnose spurdog

9a) Caudal peduncle with one or more keels or ridges........................................................ 10

9b) Caudal peduncle without keels or ridges...................................................................... 17

10a) Two keels present, a strong keel on caudal peduncle and a short secondary keel on caudal base.................................................................................... Lamna nasus - porbeagle

10b) One keel or ridge on caudal peduncle, no secondary keel on caudal base................... 11

11a) Mouth located on tip of snout; coloration a series of round spots and narrow transverse stripes; three to four large ridges along back and sides.............. Rhincodon typus - whale shark

11b) Mouth inferior; color not as above; no such ridges along back and sides ..................... 12

12a) Keel on caudal peduncle a weakly developed ridge..................................................... 13

12b) Keel on caudal peduncle well developed..................................................................... 14

13a) Spiracle present; first dorsal fin originates even with rear bases of pectoral fins; pectoral fins moderately long; coloration irregular bands or elongated spots....................................................................................... Galeocerdo cuvier - tiger shark

13b) Spiracle absent; first dorsal fin originates well past rear bases of pectoral fins; pectoral fins very long; coloration uniformly cobalt blue.............................. Prionace glauca - blue shark

14a) Gill slits long, extending almost full height of head; teeth minute and hooked........................................................................... Cetorhinus maximus - basking shark

14b) Gill slits shorter, not extending full height of head; teeth large, prominent and erect..... 15

15a) Origin of anal fin placed well behind rear base of second dorsal fin; all teeth strongly serrated, the uppers flat and broadly triangular; black spot usually present in axils of pectoral fins; coloration dark grey above and laterally with a white belly and underside of snout.............................................................................. Carcharodon carcharias - white shark

15b) Origin of anal fin placed at mid or rear base of the second dorsal fin; teeth smooth-edged, not greatly flattened, narrowly triangular and blade-like; black axil spot always lacking; coloration cobalt blue above and laterally with belly and underside of snout white................ 16

16a) Snout greatly pointed; pectoral fins much shorter than head; anal fin origin under mid base of second dorsal fin; symphysial teeth of both jaws recurved; eyes small.................................................................................... Isurus oxyrinchus - shortfin mako

16b) Snout bluntly pointed; pectoral fins as long as head; anal fin origin under rear base of second dorsal fin; symphysial teeth straight or only slightly recurved; eye large ...........................................................................................Isurus paucus - longfin mako

17a) Head flattened dorso-ventrally and expanded laterally, hammer- or spade-shaped........ 18

17b) Head not dorso-ventrally flattened and expanded laterally............................................ 21

18a) Head margin rounded, spade-shaped................................... Sphyrna tiburo - bonnethead

18b) Head hammer-shaped............................................................................................... 19

19a) Head margin broadly convex without a noticeable indentation at tip of snout.......................................................................... Sphyrna zygaena - smooth hammerhead

19b) Head margin broadly convex to straight with noticeable indentation at tip of snout....... 20

20a) Second dorsal fin small, free rear tip about twice the vertical height of fin; first dorsal fin tall, narrowly pointed, posterior margin strongly falcate; pelvic fin margin straight to weakly falcate........................................................................ Sphyrna lewini - scalloped hammerhead

20b) Second dorsal fin large, free rear tip,shorter or equal to vertical height of fin; first dorsal broadly triangular, posterior margin nearly straight to slightly falcate; pelvic fin margin strongly falcate........................................................................ Sphyrna mokarran - great hammerhead

21a) Dorsal lobe of caudal fin greatly elongated, being nearly as long as the distance from tip of snout to precaudal pit................................................................................................... 22

21b) Dorsal lobe of caudal fin not elongated, being much shorter that the distance from tip of snout to precaudal pit....................................................................................................... 23

22a) Head flattened between eyes with a pronounced, deep groove on nape above gill slits; eEyes very large, horizontal diameter is less than vertical diameter, with orbits extending onto top of head; rear tip first dorsal fin origin lies midway between rear pectoral fin base and terminates anterior to origin of pelvic fins ..................... Alopias superciliosus - bigeye thresher

22b) Head arched between eyes, no grooves present on nape above gill slits; eEye smaller, horizontal diameter is approximately equal to vertical diameter, not extending onto top of head; rear tip first dorsal fin origin lies much closer to rear pectoral fin base than toterminates over or beyond origin of pelvic fins ................................................ Alopias vulpinus - thresher

23a) First and second dorsal fins of about equal in size .................................................... 24

23b) The two dorsal fins unequal in size, the first noticeably larger than the second ........... 28

24a) A low dermal ridge present on midline of dorsal surface between first and second dorsal fins ................................................................................................................................. 25

24b) No low dorsal dermal ridge present on midline of dorsal surface between first and second dorsal fins ........................................................................................................... 26

25a) Upper labial furrows shorter than lower labial furrows; corner of lower lobe of caudal fin pointed and directed rearward; distal margin of pectoral fin deeply concave .................................................................. Mustelus norrisi - narrowfin smoothhound

25b) Upper labial furrows slightly longer than lower labial furrows; corner of lower lobe of caudal fin broadly rounded; distal margin of pectoral fin nearly straight ................................................................................. Mustelus canis - smooth dogfish

26a) Head pointed; large pointed and recurved teeth protrude from mouth .............................................................................. Carcharias taurus - sand tiger shark

26b) Head blunt; teeth pointed but not recurved or protruding from mouth............................ 27

27a) Large and obvious barbel present on margin of each nostril; no precaudal pit; teeth pavement-like with central ridge .................................... Ginglymostoma cirratum - nurse shark

27b) No barbel on margin of each nostril; precaudal pit present; teeth erect with serrations on larger individuals, smooth on young .................................. Negaprion brevirostris - lemon shark

28a) Dorsal, pectoral, and caudal fins tipped with white (black tipped in juveniles); first dorsal fin broadly rounded; pectoral fins large, paddle-shaped with rounded tips .............................................................. Carcharhinus longimanus - oceanic whitetip shark

28b) Fins not white tipped, first dorsal and pectoral fins not broadly rounded ...................... 29

29a) Anal fin origin anterior to second dorsal fin origin; larger individuals with white lateral spotting; pectoral fins with white margins
............................................................. Rhizoprionodon terraenovae - Atlantic sharpnose shark

29b) Anal fin origin posterior to or even with second dorsal fin origin; lateral white spotting lacking at all sizes ........................................................................................................... 30

30a) Low ridge present between first and second dorsal fins ............................................. 31

30b) Low ridge absent between first and second dorsal fins .............................................. 37

31a) Length of fin near tip of second dorsal fin more than two times the vertical height of the fin; first dorsal fin short with rounded tip .......................... Carcharhinus falciformis - silky shark

31b) Length of free tip of second dorsal fin in two times or less vertical height of the fin; first dorsal fin taller and not notably rounded ............................................................................ 32

32a) Snout long and pointed, distance between nostrils on underside of snout is 0.5-0.6 the length of the snout; eyes large and green in life.................. Carcharhinus signatus - night shark

32b) Snout shorter and broader, distance between nostrils on underside of snout is greater than 0.6 the length of the snout (tip of snout to mouth); eyes smaller and never green in life .................................................................................................................................. 33

33a) First dorsal fin located forward on body, its origin over or anterior to pectoral fin axil (or at least closer to the axil than to its free rear tip)- ............................................................ 34

33b) First dorsal fin located farther back on body, its origin over or posterior to the free rear tip of the pectoral fin (or at least closer to free rear tip than to axil) ................................... 35

34a) First dorsal fin large, vertical height greater than 10% of total length; snout moderately long and rounded, its length about half the height of the first dorsal fin ............................................................................. Carcharhinus plumbeus - sandbar shark

34b) First dorsal fin smaller, vertical height less than 10% of total length; snout longer and rounded or bluntly pointed, its length almost the same as the height of the first dorsal fin ................................................................................. Carcharhinus altimus - bignose shark

35a) Free rear tip of second dorsal fin short, its length about equal to the height of the fin; color grayish brown to olive gray in life with pronounced dark edging on margins of caudal fin, especially the lower lobe, and on tips of anal and second; snout short and broadly rounded; upper teeth with narrow cusps, 13 upper teeth and 12 lower teeth on each side of the jaw ....................................................................... Carcharhinus perezi - Caribbean reef shark

35b) Free rear tip of second dorsal fin longer, its length nearly 1.5 the height of the fin; color grayish brown to gray in life without pronounced dark edging on margins of caudal fin, especially the lower lobe, and on tips of anal and second dorsal fin;dorsal fin; snout moderately long; upper teeth with narrow cusps, 13 upper teeth and 12 lower teeth on each side of the jaw ................................................................................................................ 36

36a) First dorsal fin high with nearly straight anterior margin and pointed tip, snout length about 3/4 or less of the fin height in all sizes; second dorsal fin somewhat larger, length of its free rear tip 1.3-1.7 times its height .................... Carcharhinus galapagensis - Galapagos shark

36b) First dorsal fin lower with a rounded anterior margin and slightly rounded tip, snout length about equal to or greater than the fin height in all but large adults; size of second dorsal fin somewhat smaller, length of its free rear tip 1.6-2.1 times its height .............................................................................Carcharhinus obscurus - dusky shark

37a) Snout short and broadly rounded,length of snout much shorter than width of mouth; upper teeth broadly triangular and serrated, without notches on outer margins ................................................................................ Carcharhinus leucas - bull shark

37b) Snout longer, length of snout equal to or longer than width of mouth; upper teeth erect and smooth or with fine serrations, or with narrow, oblique cusps and serrated edges ............................................................................................................................. 38

38a) Black or dusky spot on tip of snout, more prominent in young and more diffuse in larger individuals; coloration yellowish green to brownish in life, fading to grey after death; teeth with narrow, oblique cusps and serrated edges ............... Carcharhinus acronotus - blacknose shark

38b) No black or dusky spot on tip of snout; teeth erect and smooth or with fine serrations . 39

39a) No black or dusky tips on fins; teeth erect, narrow, and smooth ......................................................................... Carcharhinus isodon - finetooth shark

39b) Black or dusky tips on fins; teeth with broader base and fine serrations ...................... 40

40a) Anal fin with black tip except in young (less than 70 cm total length); first dorsal fin origin lies at level of or behind free tip of pectoral fin; snout long; height of first dorsal fin less than length of snout except in large adults, when it become about the same or slightly larger; eye small, horizontal diameter is one-fourth or less than the length of first gill opening ..................................................................... Carcharhinus brevipinna - spinner shark

40b) Snout shorter; height of first dorsal fin always greater than length of snout, snout about 2/3 of first dorsal fin height in large adults; eye larger, horizontal diameter one third greater than length of first gill opening ....................................... Carcharhinus limbatus - blacktip shark