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Characteristics, distribution and ecology
Taxonomische classification
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Author: (Müller and Henle, 1839)

Field Marks:
An unmistakable requiem shark, with an extremely long, flattened, acutely pointed, triangular snout, minute circular eyes with nictitating eyelids, very large, paddle-shaped pectoral fins, the first dorsal fin with its origin over the pectoral fins, narrow, erectcusped small teeth, without cusplets, in both jaws, upper teeth serrated, and over 45 rows of teeth in both jaws, and colour grey or yellow-grey above and white below, without prominent markings. This shark bears a superficial resemblance to rhinochimaerids, the goblin shark (Mitsukurina) and certain undescribed species of the scyliorhinid genus Apristurus, all of which have similar long snouts.

Diagnostic Features:
Body fairly stout. Head narrow and flattened but not trowel-shaped; snout acutely triangular or subtriangular in dorsoventral view and very long, with preoral length much greater than internarial space and mouth width; eyes extremely small, without posterior notches; spiracles absent; no papillose gillrakers on internal gill openings; nostrils small, internarial space about 3 times the nostril width; anterior nasal flaps vestigial, not tubular; labial furrows short but prominent, essentially confined to mouth corners, with uppers about equal to lowers and with their anterior ends falling far behind eyes; teeth not strongly differentiated in upper and lower jaws, anteroposteriors with more or less erect, narrow acute cusps, no cusplets, and proximal and distal blades; uppers with slightly broader flatter cusps and serrations; lowers with slenderer cusps and smooth edges; cusps of lower teeth not protruding when mouth is closed; 49 to 60/49 to 56 rows of teeth. Interdorsal ridge absent; no lateral keels on caudal peduncle; upper precaudal pit transverse and crescentic. First dorsal origin far forward, over midbase or second third of pectoral bases, its midbase much closer to pectoral bases than to pelvics and free rear tip well anterior to pelvic fin origins; second dorsal fin considerably smaller than first but rather large, its height about 1/2 of first dorsal height, its origin slightly anterior or opposite anal origin; pectoral fins broad and triangular, their lengths from origin to free rear tip about 3/4 of pectoral anterior margins; pectoral origins about under 5th gill slit; anal fin somewhat smaller than second dorsal, with preanal ridges very short and a deeply notched posterior margin. Colour grey or brownish above, without a colour pattern. Moderatesized sharks, adults probably not exceeding 1.6 m.

Geographical Distribution:
Western Atlantic: Trinidad, Guayana, Surinam, French Guinea, probably central Brazil (Valenca, Bahaia)

Habitat and Biology:
A bizarre, little-known, inshore tropical shark of continental waters of Atlantic South America. Described as commonly frequenting estuaries and river mouths, and occurring over rocky bottoms.

This is a viviparous species, with a yolk-sac placenta; number of young recorded as 4 per litter.

The daggernose shark feeds on small schooling fishes including herring, anchovies and croakers, for which its long jaws and small, spikelike teeth are very well suited. Its small eyes and very long snout may be adaptations for feeding in turbid water, emphasizing rostral sense organs over sight.

This shark is not known to be dangerous to people, and its small teeth and small size suggest that it is an innocuous fish-eater.

Size:
Maximum said to be about 200 to 244 cm, but not verified above 152 cm, males adolescent at about 96 cm and adult at 108 cm; size at birth about 38 to 41 cm.

Interest to Fisheries:
Limited, apparently taken in small numbers by local fishermen in Trinidad, the Guayanas, and apparently central Brazil, where it is an incidental byzatch of other fisheries. Caught in fixed bottom gillnets and longlines. Occasionally marketed, but not considered a prime food fish.

Type material:
Syntypes: Rijksmuseum van Natuurlijke Historie, Leiden. Type Locality: Surinam.

Daggernose shark (Isogomphodon oxyrhynchus)