Yep I've read about the coelcanth, right in southern Africa if I remember correctly? Quite a big fish too, kind of hard to miss. I was also watching this show on jellyfish one day, and they showed some video of a colony of 4 or 5 long crimson red and reddish-brown jelly fish, about 15-20 feet long and very bulky, that have only been seen that one time. I also saw a computer generated version of a giant squid, that was in theoretical adult size, and a human is basically the size of its pupil.
No doubt are there things we haven't discovered, from the 90% of the rain forests in South America to the canyons in the see that are a thousand times larger than the Grand Canyon. It's amazing.
Oh and last I heard, humans were the top predator in Africa

And I mean we DID come from apes, right? It's not so far fetched.
-------Edit
Something we're more familiar with:
Another thing is crested geckos, they were thought to be extinct for over a hundred years, then rediscovered in 1994. They're a pretty large gecko if you ask me and so prolific. There's thousands of them in captivity today from something that was thought to be extinct.
And also wasn't there a tribe of humans in Africa discovered in the early 90s, it had no idea of an outside world existing. I remember watching that on the news, was really cool. Another thing I'll never forget watching on the global news was in India when the Ganesh statues were drinking milk from spoons. That was in 1998, and THAT was cool!
-Brock