After sleeping for some time below the Earth's crust Godzilla dug himself to the surface to find himself enigmatically in the time of Dinosaurs, possibly during the late Cretaceous period. However, the King of the Monsters was not the only visitor to this place. A horrific creature simply known as "Stranger" was also in the area, possibly looking for food. After attacking a nearby Triceratops, the Stranger noticed Godzilla. Realizing that Godzilla was the challenge it was looking for Stranger, attacked the Kaiju. While the two monsters grappled with one another they failed to notice a large asteroid streaking towards them.
Eventually the asteroid struck the ground, the Stranger attempted to flee the destruction wrought by the asteroids impact, having it's tail torn off by Godzilla in the process. As Stranger fled Godzilla burrowed beneath the Earth where he collapsed due to exhaustion.
When Godzilla awoke he once again found himself in his proper time period. At first it seemed the entire battle with Stranger was simply a dream, until Godzilla looked downward and saw he was clutching the severed tail of the Stranger.
It is possible the Stranger was of alien origin, or at least was an undiscovered species of dinosaur.
Although the "Stranger" did not posses any ranged weapons such as an energy beam, the Stranger was still a very formidable adversary, going toe-to-toe in its battle against Godzilla. The Stranger possessed an extremely durable hide that was able to resist Godzilla's atomic ray to some degree; massive wings that gave it the power of flight; a large horn which could possibly be used for combat purposes; and sharp talons which were able to easily cut through Godzilla's tough, scaly hide.