Gars (or garpike) are members of the Lepisosteiformes (or Semionotiformes), an ancient order of ray-finned fish. The family Lepisosteidae includes seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine, waters of eastern North America, Central America and the Caribbean islands. Gars have elongated bodies that are heavily armored with ganoid scales, and fronted by similarly elongated jaws filled with long, sharp teeth. All the gars are relatively large fish, but the alligator gar (Atractosteus spatula) is the largest, as specimens have been recorded up to 3 m (9.8 ft) in length. Unusually, their vascularised swim bladders can function as lungs, and most gars surface periodically to take a gulp of air. Gar flesh is edible and the hard skin and scales of gars are used by humans. Gars tend to be slow-moving fish except when striking at their prey. They prefer the shallow and weedy areas of rivers, lakes, and bayous, often congregating in small groups. They are voracious predators, catching their prey with their needle-like teeth, obtained with a sideways strike of the head. They feed extensively on smaller fish and invertebrates such as crabs. Gars are found across all of North America. Although gars are primarily found in freshwater habitats, several species enter brackish waters and a few, most notably Atractosteus tristoechus, are sometimes found in the sea. Some gars travel from lakes and rivers through sewers to get to ponds.