The Dinosaurs are the main enemies from Prehistoric Isle in 1930 and it's sequel Prehistoric Isle 2.
In the first game, set in the year 1930 A.D., the Dinosaurs are shown inhabiting a small island in the center of the Bermuda Triangle, where many ships were reported to have mysteriously disappeared. An expedition is sent to the area to investigate, dispatching two biplanes to lead reconnaissance. Upon arriving on the island, the two biplanes are immediately attacked by the dinosaurs and other hostile prehistoric creatures, forcing the pilots to fight them to explore the island.
For the most part, the dinosaurs in this game display some level of mutation, as some are shown to be way larger than their real life counterparts and are able to shoot fireballs. Aside from the usual stock dinosaurs (pterodactyls, velociraptors, etc) you also face other prehistoric creatures such as cavemen, insects and molluscs. The final boss is a gigantic Tyranossaurus larger than every other dinosaur in the game.
After defeating the Tyrannosaur, the biplanes escape the island and return to their carrier, deciding to report their finding to their leaders. However, as the expedition attempts to leave the Triangle, they are swarmed by pterosaurs who destroy the carrier ship. As such, the mystery of the Bermuda Triangle is left unresolved.
Prehistoric Isle 2
In the second game, the dinosaurs suddenly attack a city, prompting the government to send two helicopters to track down the dinosaurs and rescue any survivors. The two pilots destroy the dinosaurs in the city and follow them through some ruins, reaching an island from where they are seemingly coming from.
Despite you facing the usual dinosaurs in the beginning, as you advance through the game they become more alien-like in their appearances, not really resembling any known dinosaur. The final boss is a grotesque squid-like monster which emerges from a volcano in the middle of the island.