Thylacine

I'm a marsupial and a predator, sometimes called the Tasmanian Wolf or the Tasmanian Tiger (or, if you want to get formal about it, Thylacinus cynocephalus!). I've got lovely stripes, and I can open my jaw really, really wide! I have a bad reputation for killing sheep, and the Australian government once put a bounty on my head. That's part of why I haven't been seen since 1936. You never know, though...