Do Christians believe in dinosaurs? I don't think dinosaurs are mentioned in the Bible, which I guess means they don't, because the Bible is the source of all knowledge and truth. But I suppose they could argue that dinosaurs were created by God but were wiped out in the great flood because they were evil -- or perhaps because they wouldn't fit on the ark that Noah built. Or maybe they just couldn't swim.
Or maybe God just made the world with all those fossils under the soil to test our faith.