Archaeopteryx

The Archaeopteryx is an unmade kaiju that was meant to fight Godzilla in the unmade Godzilla vs Mechani-Kong film.

History
Not much is known about the role it would have had or how long it would have lasted in it's debut film, but early script ideas for the film involved a normal bird mutating into the monster from the radiation that leaked off of the new Mechani-Kong. It was meant to fight Godzilla in L.A.

Trivia

 * Like Deutalios, Archaeopteryx was possibly only meant to show how much stronger Godzilla was in the newer series of films.
 * Rodan's original design was that of an Archaeopteryx before they settled on using a Pteranodon.
 * In one of the Toho books, the image of it fighting Godzilla was labeled "Godzilla vs Gigamoth."