Dragon
Dragons are large reptilian, fire-breathing monsters. Though on modern-day Earth, they are considered mythological creatures by native humans, real specimens have been known to exist.
Dragons can be bipedal, quadrupedal, winged, have necks of various size, and have heads or tails in ranging numbers. Indeed, since the term "dragon" is so generic, it seems possible to describe creatures not native to Earth which fall under the very forgiving criteria as dragons.
Fiction
Generation 1 animated continuity
At least one full-on dragon (reptilian, fire-breathing, winged) has been seen on Earth in medieval times, and a similar but less imposing creature (supposedly from Borneo) in the modern era. The medieval dragon was tremendous in size, dwarfing both humans and averaged-sized Transformers. Although quite dangerous, it was driven off by a wizard using dragon's bane.
Lord Chumley spent years patiently stalking the Template:Tooltip of Borneo before transporting it back to his estate. He later set it against the captive Optimus Prime. Kinabalu was a little larger than Prime, had no wings, and did not breathe fire. It attacked him with teeth and claws, but Prime threw it off a bridge.
Also, the fictional movie monster Hojoni bears a striking resemblance to the medieval dragon, though wingless.
The only known instance of a non-Terran dragon was in the dimension of Menonia, where a wizard called the Golden One could use magic to take on the form of a large, flying golden dragon.
Beast Wars
When the Predacon Megatron took on the spark of his Decepticon namesake and was submersed in lava, his form mutated from a Tyrannosaurus rex to a large, red, fire-breathing dragon, possibly hinting at an evolutionary connection between dinosaurs and dragons.
Galvatron had the computer on Gaia(future earth) download the most powerful creatures from the planets past, which resulted in the dna of a dragon being downloaded into his system along with advanced technology, resulting in a partly cyubernetic, partly organic beast mode. This dragonmay confirm the species existance as a species, as it didn't match the dragon from mideval times....since it was pink...I mean salmon..
Unicron Trilogy
The leader of Jungle Planet, Scourge, transformed into a mechanical dragon with the ability to deploy up to three heads. Though the Jungle Planet is populated entirely by Transformers who transform into mechanical beast modes seemingly modeled after Earth creatures, it is unknown if Scourge's alt-mode has any direct connection to mythological dragons of Earth.
