In prehistory, giant animals roamed the North American continent. The Pleistocene megafauna (see Wikipedia's definition) included: giant sloths, short faced bears, California tapirs, peccaries, the American lion, giant condors, American cheetahs, saber-toothed cats (like Smilodon and the scimitar cat, Homotherium), dire wolves, saiga, camelids (such as two species of now extinct llamas and Camelops), at least two species of bison, stag-moose, the shrub-ox and Harlan's muskox, horses, mammoths and mastodons, and giant beavers. The only remaining of these today is the bison, and those in small numbers. The giant beavers interest me the most.
The megafauna died out sometime around 10,000 B.C. in a Quaternary extinction event, possibly occasioned by climatic change, human hunting, or disease. Their extinction relatively coincided with the spread of humans out of Africa and southern Asia, the only continents today that retain some diversity of megafauna.
