Progress Report 1: What are dragons?

I looked through the science section of the Library of Suraphan today. It wasn't as large as I'd hoped it'd be, but I think I got somewhere!
Archaeological records suggest dragons, or "Wishmakers", as their name directly translates to in Common, went extinct around Year 0. Fossils and bones have been found, but there's no documentation suggest they've lived any time in the past two millennia. These bones are mostly kept in monasteries and other religious places.
If Xergal wasn't so loud with his breathing, I might've been able to copy down more than one anatomy diagram! But this was all I could get. Problem is, dragons can shapeshift. So if I met a dragon, would I really recognize it? Plenty of scaled creatures also resemble dragons, including Dragonborn themselves.
These Wishmakers can generate their own magical energy. All other spellcasters draw magical energy from somewhere, whether the ambient air or borrowed from a divine entity. But Wishmakers can create their own energy. This seems counter-intuitive to basic science.