TEETH The alligator gar has a savage collection of teeth, which it uses to grab and manipulate prey as it feeds. A double row of teeth on the upper bill distinguishes the alligator gar from other members of the genus.
SCALES The alligator gar's hard scales fit together like the tesserae of a mosaic to form an armorlike shell. Covered with a durable substance called ganoine, similar to tooth enamel, these scales were used as arrowheads by Native Americans.
AIR BLADDER Thick, spongy, and highly vascular, the gar's air bladder behaves like a lung to aerate the fish's blood. It has a connection to the throat, through which the gar can "breathe" when it breaks the surface. This adaptation allows the fish to live in turbid, stagnant waters low in dissolved oxygen: under such conditions, it may obtain as much as 70 percent of the oxygen it needs from the atmosphere.
VERTEBRAE The bones of the gar's spine fit together like a series of ball-and-socket joints--a feature unique among fishes and common to reptiles and amphibians. This lets the gar move its head in an alligator-like fashion, violently nodding and thrashing to help it devour prey.
SKELETON Because of its unique skeletal composition--a curious mix of cartilage and bone--ichthyologists believe the gar to be an ancient link between the cartilaginous sharks and bony fish.