The absence of knowledge on Dragons in the era of The Allagan Empire lead me to assume that Meracydian Civilization was the precursor to other Dragon Civilizations that followed. IE, The Dragons of Dravania.

You are right to say that this is pure assumption that cannot be taken for granted. I can't recall where reading this, but I want to say that there was lore evidence that none of the spoken races are actually native to the continent/region of Eorzea. I believe this leads back to an Elezen belief that they were the first people to establish what could be called a civilization in Eorzea. And I seem to recall there being some evidence that the Roegadyn migrated by sea from the west, which is why there is still such a concentration of them on Vylbrand and the southern-most mountainous regions of Eorzea. I seem to remember also reading that the Lalafell migrated from islands to the south, explaining why there are fewer of them in the northern nations on Eorzea. Do these things actually have in game sources, or am I pulling this all out of my ass? Because I swear that this has been discussed here before, and that these facts are corroborated in item descriptions or fate descriptions and other, similar places we tend to find interesting lore bits. Like Fish. It's explicitly stated that the Miqo'te migrated in one big wave across bridges of ice in the umbral era of ice. The Hyur, I want to say, came in 3 great waves of migration by sea during an umbral era that brought great floods.

If none of the spoken races are actually native to Eorzea, I'd call that evidence that the Dravanians aren't native, either. Maybe not conclusive evidence, but consider what we DO know about the Meracydians. Huge Dragon civilization. Big enough to pose a problem to The Allagan Empire, apex civilization of its time. If all other Dragon Civilizations come from one, it's probably the one that was known to have been the most numerous and advanced in recorded history.

Just a thought. I'd like to hear some corroboration about the history of the spoken races on Eorzea if any of y'all can give me some. I'd appreciate it very much. I miss this stuff far too easily.