Proto-dragon

Proto-dragons were a genus of prehistoric lizard-like creatures from whom many scholars believed all species of dragonkind evolved.

History
It was widely believed by scholars from Candlekeep that proto-dragons were related to the prehistoric behemoths, and it was speculated that maybe it was a divergent evolved species. The first known proto-dragons were believed to be the eodracos, wyvern-like wingless creatures considered non-intelligent but more cunning than normal animals. Eodracos were able to survive the cataclysm that destroyed most of the behemoths species (believed by most the be the Tearfall, although many counter-theories existed), and began a process of evolution that lasted thousands of years, spawning a lot of proto-draconic subspecies in the process, such as the ancestors of wyverns, drakes, and pseudodragons.

Due to harsh climatic changes Toril experienced on the final years of the Days of Thunder, scholars theorized eodracos rapid evolved into two main subspecies. One which was fairly similar in nature with behemoths and was believed to be extinct, and other, named ignidracos, that had the ability to regurgitate intestinal gas and ignite it with an enzymatic, hypergolic reaction, and thus was able to breathe out blasts of fire. It was also believed ignidracos were actually intelligent and self-aware creatures, and some scholars attributed to them the creation of the draconic language.

Although scholars were unsure of how and why it happened, ignidracos evolved further into another two new species: the inficedracos, believed to the ancestors of chromatic dragons; and the ferrodracos, believed to be the ancestors of metallic dragons. Ferrodracos favored intelligence over the feral savagery of their inficedracos cousins, and developed a greater intelligence. Both genera continued to undergo process of rapid evolution, until they became the members of the species known as true dragons.

The theories about the proto-dragons weren't widely accepted by most scholars, however, and many draconic species weren't covered by its intricate evolution trees. Some apologist of the proto-dragon theory even went as far as to speculate without any kind of proof the existence of more sub-species, such as the eodraco orientalis, in an attempt to explain the existence of the species not covered by the proto-dragon theory.

Sub-races
Those were the proto-dragons species believed to have existed by suporters of the proto-draco theory:
 * Eodracos: Widely believed to be the first members of the species.
 * eodracos orientalis: An offshoot of the eodracos believed to be the ancestors of the lung dragons.
 * An offshoot that evolved into the wyverns.
 * An offshoot that evolved into the drakes.
 * An offshoot that evolved into the pseudodragons, and possibly into the faerie dragons as well.
 * A multi-headed offshoot that evolved into the hydras
 * An offshoot that went extinct
 * Ignidracos: Believed to be the first intelligent draconic ancestor
 * Ferrodracos: Believed to be the ancestor of metallic dragons
 * Inficedracos: Believed to be the ancestor of chromatic dragons
 * An offshoot that evolved into the planar dragons