Palaeophis is the first creature that existed outside the Mesozoic era to be confirmed for Beasts of Bermuda. See here for a full list of confirmed, discussed, and likely creature additions to the game.
This giant sea snake lived in the Cretaceous era and Eocene epoch. Being a sea snake, it was very likely accustomed to living and preying on the creatures of the open ocean. It was a carnivore, and is currently planned to function as a semi-aquatic creature in the game. Its in-game abilities are still being decided upon, but it is a possibility that it may feature venom. It is very likely that this creature will not be playable for the public in quite some time.