Rodan is a fictional Japanese mutated pterosaur introduced in Rodan, a 1956 release from Toho Studios, the company that produced the Godzilla series. Like Godzilla and Anguirus, he is designed after a type of prehistoric reptile (the Japanese name "Radon" is a contraction of "pteranodon"). Radon is usually referred to as "Rodan" in the United States, possibly to avoid confusion with the atomic element Radon; any time his name is written in English in Japan, it is written as Rodan. He is occasionally portrayed as a rival and enemy of Godzilla, but is usually depicted as one of Godzilla's allies, much like Anguirus. Rodan and Anguirus both started out as enemies of Godzilla, which explains the occasional enmity between the creatures and Godzilla himself on the rare occasion that they are pitted against one another.
Rodan first emerged in 1956 from a giant egg that lay underground in a mountainside. A group of miners had dug up and released a swarm of ancient bugs known as Meganulon. Once hatched the infant Rodan began feeding on the insects. It took only days for Rodan to reach its full size. It grew large horns on the back of its head and sharp serrated spikes on its chest. Rodan's skin is dark brown in color, although after turning into Fire Rodan in the Heisei film Godzilla vs. Mechagodzilla II Rodan's skin turned brick red. In the Showa and Millennium eras Rodan stood as tall as Godzilla but in the Heisei era Rodan and Fire Rodan stood only about 2/3 as tall as Godzilla. In the Heisei era the prominent rows of spines on his belly are replaced with overlapping ridges of bone and he has three horns on his head instead of two (the outer two curve outwards and the center curves up) as well as a wider beak and a more predatory face. Millennium Rodan looked more like the Showa version as it retained the Heisei era ridges of bone on its chest. It also had only two horns again, and its color is similar to the Showa version.
Rodan has layers of spikes on its chest that can be used as a weapon. In the film Ghidorah, the Three-Headed Monster Rodan slammed into Godzilla at full speed and its chest colliding with Godzilla's head to send the behemoth crashing to the ground. Rodan was once one of the fastest known Kaiju but now unfortunately he is one of the slowest flying Kaiju in the series, flying at mach 1.5. The Heisei incarnation flies at mach 3 and others such as Megaguirus fly at mach 4. But one thing most other flying Kaiju lack is Rodan's ability to emit sonic booms from its body, destroying any and all structures in its path. Sometimes called merely hurricane winds, it is clearly visible in Godzilla: Final Wars that Rodan can choose to emit the sonic booms, as demonstrated when it flew over the ship "Rumbling" and released a sonic boom destroying the air craft.
In the 1956 film Rodan was given another weapon that was never used again, a concentrated blast of wind from its mouth. This ability was most likely never used again because it was too much like Godzilla's atomic breath. An in-universe explanation can be that the Rodans from the 1956 film died in a volcano, leaving their one and only offspring to survive throughout the entire Godzilla series. The infant lacked the ability to fire a concentrated blast of wind. Fire Rodan was able to fire a uranium heat beam from its mouth, an ability acquired from Godzilla. Fire Rodan could also instill energy in others by sacrificing itself, putting its life force into another being to bring them back from the dead.