Unnamed Seadragonus Giganticus Maximus

An Unnamed Seadragonus Giganticus Maximus appeared briefly in How to Train Your Dragon.

Washed Ashore
The Unnamed Seadragonus Giganticus Maximus lay in a Sleep Coma underneath the ocean for an unknown amount of time. However a violent storm on Thor'sdat Thursday disrupted its sleep and moved it to the Long Beach on the Isle of Berk, along with another Seadragonus Giganticus Maximus, the Green Death.

"The great storm lifted both Dragons gently from the sea bed like a couple of sleeping babies, and washed them on the swell of one indescribably enormous wave onto the Long Beach, outside Hiccup's village."

- Book 1

Demise
"Tell IT. The larger Dragon has eaten the smaller one. I didn't like to interrupt."

- Stoick

After being washed ashore, the hungry Green Death ate the Unnamed Seadragonus Giganticus Maximus without much of a fight. As it was digested, it became a "Singing Supper".

Physical Appearance
The Unnamed Seadragonus Giganticus Maximus is very large, but not as large as the Green Death.

"The first dragon was averagely enormous, about the size of a large-ish cliff. The second Dragon [Green Death] was gobsmackingly vast."

- Book 1

"The first Dragon was enough to give you nightmares. The second Dragon was enough to give your nightmares nightmares."

- Book 1

No other description is given other than its size.