Well, before I start delving too deeply into the science of dinosaurs n the old west, I'm trying to hammer out some basic setting background.

Right now I'm working off a shadowrun style concept. So it's earth, and it follows history normally until right around the time the west of the united states was being settled. So round the mid to late 1700's. That's when What I am currently called the Emberfall happened and magic returned to the world. Big rifts open all over and spill some fantasy races into the world, and turmoil ensues. The east coast is torn apart in the matter of a few days. Western cities are cut off from what was considered civilization, and the entire central US becomes a no-man's land known as The Wild where monsters roam and things like Orc tribes and wild elf populations live.

The setting is focused on the west coast, with no one having had word from the east in almost one hundred years. Naturally the reappearance of dinosaurs and monsters of myth have left the local fauna devastated, so people have adapted to taming dinos instead. Trains run up and down the coast, but no longer cross the country. Only recently have people begun exhibitions into The Wild to try and cross and find out what happened on the east coast.

That's as far as I've gotten so far.