Diabloceratops

Diabloceratops eatoni is said to live on the north western side of phoenix corps island which is why it is not seen in the game. in media:

Diabloceratops appears in The survivors guide book on it's own page being said to live on the northwestern side. it is never seen alive only heard in both Story mode and the main game. The characters also walk past an acrocanthosaurus nest and see a Diabloceratops skull beside the predators eggs.