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 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 creatures considered non-intelligent but more cunning than normal animals. Eodracos were able to survive the cataclysm that destroyed most of the behemoth species (believed by most to 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. Fossil evidence also suggested the existence of winged multi-headed proto-dragons, and many believed those were the ancestors of hydras and other multi-headed reptiles.

Due to the 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 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 how and why it happened, ignidracos evolved further into another two new species: the inficedracos, believed to be the ancestors of chromatic dragons; and the ferrodracos, believed to be the ancestors of metallic dragons. Both genera continued to undergo process of rapid evolution, until they became the members of the species known as true dragons some time around -10000 DR.

Controversy
The proto-dragon theory, as this group of theories came to be known, wasn't widely accepted by most scholars and experts in draconic creatures, prominent among them those who shunned the "evolutionist" theory in favor for the simply but most widely accepted explanation of the gods as the creators of mortal races. A popular counter-theory was to point out to the existence of dragons of similar races to those found in Toril in other planets, crystal spheres, worlds, and even the Outer Planes. This counter-theory, however, was countered by supporters of the proto-dragon theory by pointing out that not only in Toril, but also in many other worlds, there was enough fossil evidence to prove the existence of the proto-dragon species. The fact that proto-dragon fossils existed in worlds beyond Toril created a lot of controversy as well.

The proto-dragon theory also had many inconsistencies and it didn't covered the origins of draconic species unrelated to the chromatic and metallic dragons. Some apologists 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 draconic species not covered by the proto-dragon theory.

Sub-races
There were many proto-dragons species believed to have existed by supporters of the proto-dragon 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, winged offshoot that evolved into hydras and dracohydras.
 * An offshoot that went extinct.
 * Ignidracos: An evolved species believed to be the first intelligent draconic creature.
 * Ferrodracos: An evolved species believed to be the ancestor of metallic dragons.
 * Inficedracos: An evolved species believed to be the ancestor of chromatic dragons.
 * An evolved species believed to have evolved into the planar dragons.