Alligator gar: The 'living fossil' that has barely evolved for 100 million years

Name: Alligator gar (Atractosteus spatula)

Where it lives: Rivers, reservoirs and coastal bays in southwestern U.S. states, down to Veracruz, Mexico

What it eats: Crabs, fish, birds, mammals, turtles, and carrion

Why it's awesome: With their long snout, thick armored scales, and two rows of piercing teeth, these huge fish could easily be mistaken for a ferocious gator — hence their common name: alligator gar.

Reeling in A HUGE Alligator Gar | ALLIGATOR GAR | River Monsters - YouTube

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They are the largest known species of gar and can grow to around 8 feet (2.4 meters).

Related: 'True rarity': Gigantic alligator gar caught and released in Texas reservoir could break 2 world records

This enormous fish is "a truly prehistoric monster," said biologist Jeremy Wade on "River Monsters." Fossils have shown that these ancient Animals existed 100 million years ago during the Cretaceous period (145 million to 66 million years ago), when dinosaurs roamed Earth.