Zoo Tycoon 2: Extinct Animals

Quagga

Release all extinct animals into the wild to unlock the Quagga.

Lab accident animals

Get an animal creation mini-game score lower than 50% to unlock one of the following animals:

Giant Bullfrog
Giant Monarch Butterfly
Killer Penguin
Red Squirrel
Springhare

Note: Except for the Killer Penguin, all of these animals are just selectable ambients.