Most animals that have ever existed are now extinct - that's how nature and evolution works.
But it's still sad to think that some varieties disappeared during the last century, or sometimes even later.
Here are a few examples of animals that don't exist anymore.
Lonesome George was the last of his kind, the Pinta Island Tortoise from the Galapagos Islands.
He died in 2012, and with his passing, his species became extinct.
Often called the "Goddess of the Yangtze," this freshwater dolphin from China went extinct due to habitat destruction and pollution.
This wild goat was native to the Pyrenees Mountains in Europe. The last one, named Celia, died in 2000, making the species extinct.
Also known as the Blue Macaw, it was native to Brazil.
Habitat loss and illegal trapping caused its extinction in the wild, but efforts are being made to reintroduce them.
This tiger, native to Indonesia, was declared extinct in the 1980s due to hunting and habitat loss.
Once found in Africa, this rhino species was hunted to extinction for its horn.
This seal used to inhabit the Caribbean Sea but hasn't been seen since the 1950s, likely due to hunting and habitat destruction.
This vibrant yellow toad from Costa Rica disappeared in the late 1980s, and scientists believe it was due to climate change and a deadly fungus.