When the last member of a species dies, they have gone extinct. There are many reasons this could happen, including disease, being out-competed, loss of habitat, or a natural disaster, like the asteroid that took out the dinosaurs.
Of course, the world is a pretty big place, and with over 7 million different species of animals, it's pretty hard to keep track of all of them. Occasionally, scientists will mistakenly declare that a species has gone extinct, though they are really alive and well.
Alltime10s has made a new video of the top 10 animals that were believed to be extinct but were actually found to be alive. Their stories are all different: some hadn't been seen in decades, others were questioned if they ever existed at all, and one was even assumed to have died out before the dinosaurs did, but they were all still here among the living.
Check out these incredible discoveries here:
Which animal are you most glad to see is still around? Let us know in the comments!