Carcharhinus isodon

Author: (Valenciennes, 1839)

Field Marks:
A small grey shark with moderately long pointed snout, fairly large eyes, snout tip, very long gill slits about half length of dorsal base, erect-cusped smooth or irregularly serrated teeth in both jaws, upper teeth without cusplets, 12 to 15/13 to 14 rows of anterolateral teeth, no interdorsal ridge, small pectoral fins, a small first dorsal with a short rear tip and a moderately large second dorsal with a short rear tip, and no prominent markings on fins.

Diagnostic Features:
A fairly slim species (up to about 2 m, but most smaller). Snout fairly long and moderately pointed; internarial width 1.3 times in preoral length; eyes circular and moderately large, their length 1.8 to 1.9% of total length; anterior nasal flaps low and broadly angular, not expanded; upper labial furrows short and inconspicuous; hyomandibular line of pores just behind mouth corners not conspicuously enlarged; giil slits very long, the third 4.8 to 5.7% of total length and about half of first dorsal base; 12 to 15/13 to 14 rows of anteroposterior teeth in each jaw half; upper teeth with narrow, weakly serrated or smooth, erect to slightly oblique cusps, and crown feet with weak serrations or none and no cusplets; lower teeth with erect, smooth cusps and transverse roots. No interdorsal ridge. First dorsal fin large and somewhat falcate, with a pointed or narrowly rounded apex and posterior margin curving ventrally from fin apex; origin of first dorsal fin over or only slightly posterior to pectoral insertions; inner margin of first dorsal moderately short, about a third of dorsal base; second dorsal fin large and high, its height 2.8 to 2.9% of total length, its inner margin short and 1.4 times its height; origin of second dorsal over or slightly posterior to anal origin; pectoral fins small, falcate, with narrowly rounded or pointed apices, length of anterior margins about 13% of total length in small individuals; 163 to 166 total vertebral centra, 77 to 81 precaudal centra. Colour plain, dark grey above, white below; no conspicuous markings on fins; an inconspicuous white band on flank.

Geographical Distribution:
Western Atlantic: North Carolina and exceptionally New York to Florida, Cuba, Gulf of Mexico; southern Brazil. ? Eastern Atlantic: Senegal and Guinea-Bissau.

Habitat and Biology:
A little-known grey shark of the tropical Atlantic, generally present close inshore. Thought to move northward along the east coast of the USA in summer. Forms large schools. Viviparous, with a yolk-sac placenta; number of young 1 to 6 per litter. Probably a predator on small bony fishes and cephalopods.

Size:
Maximum about 189 cm and possibly to 200 cm, males maturing at about 140 cm and reaching at least 158 cm, females maturing at about 150 cm and reaching at least 165 cm; size at birth 51 to 64 cm.

Interest to Fisheries:
In the western Atlantic caucht incidentally throughout its range but relatively unimportant; caught with floating longlines inshore and presumably eaten fresh and dried salted.

Remarks:
Old records of this species from tropical West Africa have not been confirmed, and it is possible that these were based on some other species, particularly C. brevipinna.

Type material:
Holotype: Museum National d'Histoire Naturelle, MNHN 1037, 650 mm immature male. Type Locality: Probably coast of New York, USA.

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