"Besides which, the Forgotten Realms is a hodgepodge creation, medieval period, ancient Egyptian, and barbarian hordes for example."
Yup, and like I keep telling people. This is a good thing. It's because the Realms are a fantasy world. Just like our real world has deserts, oceans, forests, jungles, plains, etc. all in one setting so does the Realms.
Just because dinos are instinct in 2008 Earth doesn't mean they should be extinct in the Reams/Abeir Toril. The Mainland (ie. the area that people are most familair with) are LOOSELY based on the medieval period. Like you mentioned, hwoever, the Realms have other stuff like Egyptian based dieties, and stuff. Even some of their gods like Tyr were 'stolen' / 'borowed' from random places. *shrug*