The manuscript is done, more or less, so I can pop back here and give a few more details.
1) The book takes a toolkit approach to the setting, breaking it down into elements (PRIMEVAL=time anomalies + dinosaurs + secret conspiracies) and then building a campaign out of those elements. So, you've got the ARC as your default framework, but there are three other sample setups (dinosaur safaris for the super-rich, little village under siege by dinosaurs, WWII special forces).
2) It's using a slightly tweaked version of the Doctor Who system - 95% the same, but some Traits have been changed, there are no special powers, and the system's a bit more lethal. Initiative's changed too.
3) There's a special subsystem to handle 'temporal damage'. Basically, if you change the timeline, you accrue temporal damage as a group. The GM rolls to see what effect this damage has. You may get lucky, and find that the damage has no effect, or it might stick around and stack with next week's adventure, or you end up jumping timelines and erasing people from existence.
4) Monster behaviour has its own rule system, too; different creatures have different reactions and special attacks.