Godzilla, a theropod dinousaur of the genus gojirasaurus

Radioactivity from hydrogen bomb testing at Bikini Atoll, 1954.

Highly radioactive body; leaves trail of radioactive residue.

Radioactive plasma breath/ray.

Nuclear pulse locomotion.

Increase in size from 12 meters tall, weighing 60 metric tons, to (at least) 50 meters tall and weighing 20,000 metric tons.

Ability to reproduce a-sexually.

Ability, rather necessity, to ingest radioactive materials, e.g., nuclear reactors.

Eventually, Godzilla succumbed to his own internal nuclear disaster: a combination of emotional grief over the death of his child, the stress of physical attack, and an apparent malfunction caused his atomic heart to melt-down. As the melt-down progressed it manifested itself physically in the form of glowing red patches on Godzilla's epidermis, and his normally blue radioactive breath glowed red.

An early biotechnological experiment fusing of one of Godzilla's immortal cells (G-cell) with a previously created rose/human hybrid cell created Biollante. Biollante is further mutated under the influence of Godzilla's radioactive breath. A creature capable of emitting corrosive radioactive sap...

One of Biollante's rose/human/Godzilla cells made its way into outer space where it fused with a crystalline alien [cosmic] life-form in a black hole creating SpaceGodzilla.

The intense radioactivity of Godzilla's nuclear immolation revived and further mutated his son Godzilla Junior. Godzilla Junior originally mutated from a gojirasaurus under the influence of residual radioactivity from the atomic tests in the Marshall Islands.