While the houndfish has no spines, its dorsal fin has 21–25 soft rays, and its anal fin has 19–22. They are also known to have 80–86 vertebrae. A key way of distinguishing the houndfish from other members of the genus Tylosurus is that the houndfish's teeth point anteriorly when the fish is a juvenile. The teeth of other species are straight at all ages. The houndfish also has a more stout, cylindrical body and a shorter head than other needlefishes. They have dark blue backs and silver-white sides and are plain white ventrally. A houndfish has a distinct keel on the caudal peduncle, and the caudal fin itself is deeply forked. Juvenile houndfish possess an elevated, black lobe on the posterior of their dorsal fins. The longest recorded houndfish was 150 centimetres (4. 9 ft), and the largest recorded weight was 6. 35 kilograms (14. 0 lb).
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