In this corner, weighing up to 190 metric tons, is the blue whale. This behemoth still swimming in Earth's oceans is the current titleholder for the heaviest animal to ever exist - living or dead.
And in this corner is the contender, a massive marine mammal that went extinct millions of years ago. Fossils of this ancient leviathan's bones recently dug up from the deserts of Peru suggest it may have weighed up to 340 metric tons, challenging the blue whale's status as the most massive ever in the animal kingdom.