Godzilla (1954)

"We discovered a skeleton in the Tokyo Bay resembling Godzilla, but it is much younger than the one in the Philippines.

Could this be.......another Godzilla?

I have information on the skeleton. The date of the monster's death was 1954.

You're telling me that the Godzilla that is currently living was not the Godzilla that we bombed on Castle Bravo?

Yes, sir. Japanese people say that there was a Godzilla destroying Tokyo in the same year that we launched Castle Bravo."

- Major Anthony Hicks and a informative in Godzilla: Earthright.

The 1954 Godzilla (ゴジラ, Gojira), also dubbed as the First Godzilla and the original Godzilla is a reptilian daikaiju creaed by Toho and remade by Legendary Pictures that first appeared in the series, The Monarch Files. His skeleton was seen in Godzilla: Earthright. He appeared in a flashback episode in Godzilla: Monster Wars.

Godzilla (2014) (flashback set in 1954)
Godzilla awoke in 1945 when the U.S launched an atomic bomb in Nagasaki and Hiroshima. He came ashore in 1954 at Castle Bravo and was bombed as a plan to kill the creature. This Godzilla was believed to be the Godzilla that is currently living, but this was confirmed to be false months later.

Godzilla: Monster Wars (flashback episode set in 1954)
Japanese ships were being attacked by this monster, so investigators were sent to Odo Island to find out why he's destroying these ships. Suddenly, the monster appeared over the hill. The people from Odo Island, the investigators, and tourists fled, realizing it was 259 feet.