Dragon

A big, green, fire snortin' lizard. No, not that one.

Dragons are organic lifeforms native to the planet Earth. They appear to be reptilian in nature, are capable of flight, and can breathe fire. They are also tremendous in size, dwarfing both humans and averaged-sized Transformers. Although quite dangerous, they have been known to be driven off through the use of dragon's bane.

From Teletraan I: The Transformers Wiki, a Wikia wiki.