Ignidraco

The Ignidraco was a genus of prehistoric proto-dragons.

Ecology
Scholars from Candlekeep theorized that ignidracos had an evolved digestive tract that enabled them to regurgitate intestinal gas and ignite it with an enzymatic, hypergolic reaction in the back of their throats, making them capable of breathing out blasts of fire. As the ignidracos continued evolving, some of the species began to modify their digestive tracts, developing special gastric enzymes that allowed them to spit acid, exhale corrosive chemicals, and even a chemical substance able to absorb heat to the point of freezing the air and objects around it.

History
Scholars believed that ignidracos were an evolved strain of the eodraco genus. It was theorized that certain species of ignidracos developed the first stages of self-awareness and real intelligence, not just the improved animal cunning shown by earlier species of eodracos. A few scholars believed ignidracos began to develop the earliest manifestations of the draconic language, although there was not enough evidence to prove anything. It was also believed that, as ignidracos depended mostly on their intelligence for survival, the species began to develop longer life spans.

Scholars didn't had enough evidence to theorize why it happened, but eventually ignidracos evolved into two new genera: the ferrodracos and the inficedracos.

Detractors of the proto-dragon theory believed that the fact that some species of dragons were capable of breathing out kinds of elemental energy other than fire (such as the blue dragons ability to breathe out lightning) made the theory of the evolved digestive tract illogical, and that the theory that explained the white dragons ability to breathe out frost as some sort of chemical reaction capable of absorbing heat was just rubbish.