I would think Darwin's "Origin of the Species" help contribute to the acceptance of large beast roaming the earth but then again I'm not even sure when Dinosaurs were first theorized. It must have been pretty jarring to discover bones of creatures so different from what was in the wild.
Just a clarification:
Archaeologists: Humans.
Paleontologists: Animals.
That being said, before knowing about evolution, I'd say the main theories would have been Creationism, Catastrophism and Fixism. Out of the top of my head, I can recall Georges Cuvier as a referent for the first theory and Carl Linneus for the second. Cuvier developed his theory as a form of the one of Linneus.
I think we all know about Creationism: God pretty much created things as they are, and that's that.
Linneus' theory of fixism stated that every species was created separated an unrelated to the other. He denied the possibility of a common ancestor. Every animal was created as we see it and there was no change.
Catastrophism stated that the world was some sort of etch-a-sketch, were species were created, then wiped out by catastrophes, then more were created and so on. Dinosaurs would have been remains of these extinct species of previous stages of the world.
This is a very very short and blunt summary. I apologize for not providing a more detailed answer. I hope I have provided enough information for you to continue reading and investigating.