The Problem With Bigfoot
When I see a heading like the one you just read I automatically think to myself "Like there's only one problem with Bigfoot."
Cryptozoology (the search for animals whose existence has not been proven due to lack of evidence - Wikipedia) should be feeling somewhat vindicated these days due to a few recent discoveries.
One was the definitive confirmation of the existence of the Giant Squid (Wikipedia, underwater photos from 2004, video of the giant squid that swam into Japan’s Toyama Bay in December 2015.
Another, and much simpler case is the return of cougars to areas of Eastern Canada where they were long thought extinct.
This is still up for debate with many still claiming that the Eastern Cougar disappeared over 70 years ago (Eastern Cougar declared extinct, says U.S. Fish and Wildlife Service - CBC.ca) with evidence that cougars are on the prowl, at least in parts of northern Ontario. (read Cougars are officially back in Ontario)
Whether the cougars are the original Eastern Cougar, Mountain Lions that have migrated from the west filling in territorial predator gaps or cats that were once pets now released into wild seems to be only thing up for real debate.
Other animals considered to be mythical that turned out to be real over the past 100 or so years include: