Though the Silver and Black arowanas of South America, and the Asian and Australian arowanas resemble each other, and share the behavior of brooding their eggs and fry in their mouths, they last shared a common ancestor around 170 million years ago, when the great Southern Continent Gondwana began to split apart. This took place in the Jurassic period, when dinosaurs still thrived. Although Asian arowanas are endangered, South American ones are abundant, and are important both to subsistence fishing and the sustainable aquarium trade.
Called Arapaima in the Guianas, Paiche in Peru, and Pirarucu in Brazil, this relative of the arowana is one of the largest purely freshwater fishes in the world, reaching nine feet and exceeding 400 pounds. They have been overexploited as food fishes, so are vulnerable to extinction. These fast-growing predators surface frequently to take air at the surface. While aquarium visitors may mistake them for Alligator gars, they are not related. Their closest North American relatives are the herring-like Mooneyes and Goldeneyes.