gar, member of the family Lepisosteidae, freshwater fishes found in the warmer rivers and lakes of the S United States, Central America, Mexico, and the West Indies. Gars are highly predacious and destroy many useful fish. They are cylindrical fishes with long jaws and formidable teeth; their peculiar armature of diamond-shaped platelike scales, composed of a hard inorganic salt, is often found also in fossil fish. The largest species is the 9-ft (275-cm) alligator gar of the Mississippi valley. Others are the long-nosed gar (Lepisosteus osseus), the spotted gar, and the short-nosed gar. The name garfish is sometimes used for the gar but is more correctly applied to the saltwater gar (see needlefish). Gars are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Lepisosteiformes, family Lepisosteidae.

Any of several large North or Central American fishes of the genus Lepisosteus. They are related to the bowfin and date back to the Eocene Epoch. Gars are confined chiefly to fresh water, though some species enter brackish or salt water. They frequently bask at the surface in sluggish waters and commonly breathe atmospheric air. Their jaws and face form a sharp-toothed beak, and their body is encased in an armour of diamond-shaped, thick scales. Their eggs are toxic to predators. They are highly voracious predators, with long rows of needlelike teeth. The alligator gar of the southern U.S. reaches a length of about 10 ft (3 m) and is one of the largest freshwater fishes.

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