Winghead Shark

True to its name, the winghead shark's cephalofoil consists of a pair of long, narrow, and gently swept-back blades. The width of the cephalofoil is equal to 40–50% of the shark's total length. The front of the cephalofoil has a slight indentation in the middle and a gentle bump on each side in front of the nostrils. Each nostril is roughly twice as long as the width of the mouth and extends along almost the entire leading margin of each blade. The circular eyes, located at the forward outer corners of the cephalofoil, are equipped with protective nictitating membranes. The relatively small, arched mouth contains 15–16 upper and 14 lower tooth rows on each side, and sometimes also a single row of tiny teeth at the upper and/or lower symphyses (jaw midpoints). The teeth are small and smooth-edged, with angled triangular cusps. Five pairs of gill slits are seen, with the fifth pair over the pectoral fin origins. The body is slim and streamlined, with a very tall, narrow, and falcate (sickle-shaped) first dorsal fin that originates over the bases of the rather small pectoral fins. The second dorsal fin is much smaller and originates over the caudal third of the anal fin base. The anal fin is about half again as long as the second dorsal fin. A lengthwise groove is on the caudal peduncle at the dorsal origin of the caudal fin. …

The winghead shark is found in the tropical central and western Indo-Pacific, from the Persian Gulf eastward across South and Southeast Asia to New Guinea and northern Queensland. Its range extends as far north as Taiwan and as far south as the Montebello Islands off Western Australia. This species inhabits shallow waters close to shore and has been known to enter estuaries.

Several nonexclusive hypotheses have been proposed to explain the extreme size of the winghead shark's cephalofoil. The placement of the eyes at the ends of the cephalofoil provides a binocular field of view of 48°, the most of any hammerhead and four times that of a requiem shark; this species thus has excellent depth perception, which may aid in hunting. This species also has proportionately the longest nostrils among the hammerheads; longer nostrils contain more chemosensory receptors and can sample more water at a time, increasing the chances of detecting an odor molecule. A winghead shark 1 m (3.3 ft) long is theoretically capable of sampling over 2,300 cm3 (140 in3) of water per second. Another potential olfactory benefit of the cephalofoil is increased separation between the midpoints of the left and right nostrils, which enhances the shark's ability to resolve the direction of a scent trail. Finally, the cephalofoil may increase the shark's ability to detect the electric fields and movements of its prey, by providing a larger surface area for its electroreceptive ampullae of Lorenzini and mechanoreceptive lateral line. The lateral blades seem too large to function in maneuvering, which has been suggested for other hammerheads. The winghead shark usually hunts close to the sea floor. Its diet consists mainly of small bony fishes, followed by crustaceans and cephalopods. …