Did the feathered dinosaurs of the Cretaceous period learn to fly by running on the ground or jumping from tree to tree? Here's what we know about the origins of flight among the dino-birds of the Mesozoic Era.

Illustration: Luis Rey

Though most readers insist that Megalodon would come out on top in a one-on-one matchup with Leviathan, a few still remain in Leviathan's camp. Here are some arguments in favor of the giant whale emerging as the victor.

Illustration of Leviathan: C. Letenneur

A huge assortment of dinosaurs lived in North America during the Mesozoic Era. Here's a list of the 10 most important (and most influential) North American dinosaurs, ranging from Allosaurus to Tyrannosaurus Rex.

Illustration of Diplodocus: Vladimir Nikolov

In Megalodon vs. Leviathan - Who Wins?, we examined a scenario in which a full-grown Megalodon engaged a full-grown Leviathan in one-on-one combat. In our analysis, Leviathan emerged as the winner, enraging hundreds of Megalodon fans who posted their comments and complaints. Here's the reader case in favor of Megalodon.

Illustration of Megalodon: Nobu Tamura