[Robert A Cook PE]

Sabertoothed cats would have lived alongside other extinct animals such as dire wolf, giant short-faced bear, long-nosed peccary, flat-headed peccary, stag-moose, muskox, and giant ground sloth, and maybe a few bison and mammoth.

All of which died out completely just a few years after a skinny, light-weight, biped walked across the Caucus steppes and mountains, the Siberian Plains and the Mongolian high plains, crossed the barren muddy Bering Plains and then walked down the (future) Canadian and Central US flatlands.

Man! Them little biped babies sure are tough and mean! (That, or their mothers are.)

[Red Badger]

OR

They were wiped out by a giant meteor strike in what is now northern Canada...........................

[crusty old prospector]

They died out at the end of the Ice Age. Their remains have been found all over the High Plains. Most specimens come from the La Brea tar pits.

[SunkenCiv]

All of them died out simultaneously due to, well, it’s in that book I linked up there. At least, I *think* I did... hmm...