Godzillasaurus

Godzillasaurus (ゴジラザウルス, 'Gojirazaurusu') is a strange type of dinosaur. It appeared in the Heisei series, and is accepted as what Godzilla was before being mutated by the bomb.

Overview
The Godzillasaurus is a very strange type of Tyrannosaurus looking dinosaur, standing more upright than a tyrannosaurus would, and having two rows of teeth, very much like a shark. As is shown in Godzilla vs. Mechagodzilla 2, Godzillasaurus's seem to be telepathic, seeing as Baby Godzilla can contact his father, but it is unlikely that unmutated Godzillasaurus's would have been able to do something like that.

Film Appearances
Evidently the Godzillasaurus lived out in Lagos island in Godzilla vs. King Ghidorah (Heisei), and was attacked by soldiers during World War II. This was observed by Futurians that had traveled back in time in a bid to destroy Godzilla. They transported the mortally wounded creature to the Bering Sea, believing that it would die. However, in an incident involving a nuclear submarine, the near dead Godzillasaurus became the fully powered Godzilla.

Other film appearances
Another Godzillasaurus, Godzilla Jr, is found in Rodan's nest in Godzilla vs. Mechagodzilla 2. This one seems to have been affected by nuclear energy as well, considering the fact that when it was not fully grown, it was far bigger than the seemingly adult Godzillasaurus. (This is seen in Godzilla vs. SpaceGodzilla. This Godzilla can fire nuclear blasts, and appeared to have been a herbivore in his youth. However, in Godzilla vs. Destroyah, this Godzillasaurus is seen eating whales.

Trivia

 * An actual species of Dinosaurs was named the Gojirasaurus, in homage to Godzilla himself. However, this "Godzillasaurus" does not look like the ones displayed in the movies, grown or not, mutated or not.
 * Ironically, Gamera's roar was used for the Godzillasaurus' roar