1. Large or relatively large animals, as of a particular region or period, considered as a group.
2. Creatures that had the dual virtues of being dramatically large and coexistent with prehistoric humans who hunted mammoths and mastodons.

American megafauna once included: mammoths, camels, giant short-faced bears, giant armadillos, stag moose, glyptodonts (resembling giant armadillos), saber-toothed cats, dire wolves (larger and having more massive skulls than modern wolves), giant ground sloths, and horses, among others.