1687. Seadragonus Giganticus Maximus

The Seadragonus Giganticus Maximus is a type of dragon. These "preposterously huge" fire-breathing Sea Dragons are twenty times the size of a blue whale, and are very dangerous -- they kill for sport. When a Sea Dragon appears on the beach looking for a fight, Hiccup is the only one with a plan to save the tribe.
 Sea Dragons are blue with an orange underside. They have very primitive, dinosaur-like characteristics, with heads that resemble a Tyrannosaurus, narrow sharp teeth, small frills similar to those of Triceratops, thick pillar-like legs like those of Sauropods, and a clubbed tail similar to that of Ankylosaurus. They have red spikes from the back of the neck to the tail and wings with a single membrane. They also have gigantic legs with red spikes on them and five claws on the ends. Sea Dragons are the biggest dragon species ever seen, and they can crush a whole Viking house easily.