An Unnamed Seadragonus Giganticus Maximus appeared briefly in How to Train Your Dragon.
|“||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|
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'sday 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.
|“||Tell IT. The larger Dragon has eaten the smaller one. I didn't like to interrupt.||”|
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".
|“||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 Unnamed Seadragonus Giganticus Maximus is very large, but not as large as the Green Death.
|"How to Train Your Dragon":||Mentioned||"How to Ride a Dragon's Storm":||Absent|
|"How to Be a Pirate":||Absent||"How to Break a Dragon's Heart":||Absent|
|"How to Speak Dragonese":||Absent||"How to Steal a Dragon's Sword":||Absent|
|"How to Cheat a Dragon's Curse":||Absent||"How to Seize a Dragon's Jewel":||Absent|
|"How to Twist a Dragon's Tale":||Absent||"How to Betray a Dragon's Hero":||Absent|
|"A Hero's Guide to Deadly Dragons":||Absent||"How to Fight a Dragon's Fury":||Absent|