Alligator gar

Atractosteus spatula is the largest species of gar (family Lepisosteidae) and one of the largest exclusively freshwater fishes in North America. Adults commonly reach 1.5–2 m in length and can exceed 3 m and 140 kg. The species is characterized by a massive, torpedo-shaped body, a broad, short snout bearing two rows of large, fang-like teeth in the upper jaw (distinguishing it from other gars with a single row), and a body covered in interlocking, diamond-shaped ganoid scales that form a virtually impenetrable armor. The dorsal and anal fins are positioned far posteriorly near the abbreviated heterocercal tail. Alligator gars possess a vascularized swim bladder that functions as a lung, allowing them to gulp air at the surface—an adaptation to warm, oxygen-poor waters. They inhabit large rivers, bayous, reservoirs, and coastal estuaries of the Mississippi River basin, Gulf Coast drainages, and historically north to the Ohio River. They are ambush predators feeding on fish, crabs, and waterfowl. Reproduction occurs in spring floods; eggs are toxic to mammals. Alligator gars are "living fossils," with a lineage dating back over 100 million years. Once considered nuisance fish, they are now valued for ecosystem management and sport fishing. Conservation efforts have expanded as populations declined from habitat loss and historical eradication programs.