Tiamat=dragon? Options

I would be very grateful if someone could help me find the answer to a question that's been bothering me for a while: the idea that the primordial goddess Tiamat is a "dragon" or appears in a "serpent" form seems to be quite widespread and I just can't find a source for that description. In fact, I read through a translation of the Enuma Elish and the deity wasn't described with precision (unless I missed a part of the story). So this is my question: where does that "dragon" description come from?

Wikipedia says that Tiamat's draconic form was popularized with the wondrous birth of dungeons and dragons~

My best guess is that as a female/water/yin egregore, but at the same time a creation god, the form of a dragon symbolizes the equilibrium between yin and yang forms. The dragon/snake/long-penis-like-thing generally represents a male aspect. Quetzalcoatl is often interpreted as a snake god in such respects (and is also a sex/creation god.)

I think that perhaps the division between male and female symbolism exists to show a form of semi-absolute or complete form of hermaphroditic power? I'm sort of just throwing jabs at the notion.

On the other hand, is it allegedly claimed that Tiamat existed on this plane of existence as a dragon, cavorting alongsides dinosaurs? Or complicating the bureaucratic offices of The Jade Emperor?

Sorry to topic hijack, but why is popular representation important? Couldn't we just ask them if the egregore had any power left in them?