Dragon Turtles

In the old days of Sosaria, Dragon Turtles were a real danger for all ships. Protected by their strong shell, and attacking with strong fire breath, they were very dangerous. Thankfully, with the end of Mondain, these monsters died out in Sosaria and became a terror of the past.

Dragon Turtles only appeared in Ultima I, vanished afterwards when Sosaria was thundered apart. However, one has to wonder, if the Turtle in Ultima VII/2 is a Dragon Turtle. Even if it is, all indicates that Dragon Turtles are almost extinct on Serpent Isle as well.

They are found at sea.

Notable Examples
The Turtle in Ultima VII/2 that brings the party to Erstam's isle, while not said, seems to be a Dragon Turtle, at least when considering the sheer size of the animal. This seems therefore not too far-fatched.