Alligator gar (
Atractosteus spatula) are
ray-finned euryhaline fishes related to
bowfin in the
infraclass Holostei (ho'-las-te-i). The
fossil record traces the existence of alligator gars back to the
Early Cretaceous over a hundred million years ago. They are the largest in the gar family, and among the largest freshwater fishes in
North America. Gars are often referred to as "
primitive fishes", or "
living fossils" because they have retained some
morphological characters of their earliest ancestors, such as a
spiral valve intestine which is also common to the digestive system of
sharks, and they can breathe both air and water. Their common name was derived from their resemblance to American
alligators, particularly their broad snout and long sharp teeth. Anecdotal scientific reports suggest that alligator gars can grow up to in length and weigh as much as ; however in 2011 the largest alligator gar ever caught and officially recorded was long, weighed , and was around the girth. Their bodies are torpedo shaped, usually brown or olive fading to a lighter gray or yellow
ventral surface. They do not have scales like other fish, rather they are armored for protection against predation with hard, enamel-like, jagged diamond-shaped
ganoid scales that are nearly impenetrable. Unlike other
gar species, mature alligator gars have a dual row of large sharp teeth in the upper jaw which they use for impaling and holding prey. They are stalking, ambush
predators that are primarily
piscivores, but will also ambush and eat
water fowl and small
mammals that may be floating on the surface.