Gargantosaurus

The Gargantosauruses are a race of alien shapeshifters that arrived on Earth, at the age of dinosaurs.

Biology
In their current forms, the Gargantosauruses are quadrupedal reptiles of enormous dimensions, with red scaly skin, clawed feet, a long tail and a lipless mouth full of sharp teeth.

It's unknown what they look like in their original forms, although it is implied they are made of energy.

History
65 million years ago, a species of shapeshifting extraterrestrial creatures arrived on Earth, during the Cretaceous. Many members of the species take the form of dinosaurs and mammals, in order to camouflage with the animals. When dinosaurs got extinct, the aliens lose their shapeshifting abilities and got stuck in their changed forms.

While the mammalian ones choose to interbreed with mammals, the reptilian ones refused to interbreed with the mammals and became the source of dragons, sea serpents and other mythological creatures.

Appearances

 * Saurian (1988)