a fish called the coelacanth which is now commonly found in the carribean.
Just about all animals alive today are prehistoric. The word prehistoric means before written history. Anything 5,000 years or older give or take would be prehistoric. It does sound better than Pre-Cretaceous period but that would be the last time dinosaurs we're prevelant.
Those are all modern animals that existed in prehistoric times.
Here are some animals known only from fossil evidence some believe are still alive today.
Mokele membe, a creature pygmys report to have seen in the Congo, is often considered to be a surviving population of Sauropod Dinosaurs.
The Ropen in New Guinea may be a live Pterasaur.
Some scientists speculate that the Megalodon shark still exists in the depths.
The Thunderbird sitings may be of Argentavis, a prehistoric giant bird.
As has been said, the coelacanth is a fish once thought to be long extinct, but has now been proven to exist. Why it disappeared from the fossil record remains unexplained.
And some think that a plateau in the Amazon rainforest has supported an isolated group of Dinosaurs. A "Lost World".