Just weeks before it’s supposed to head into production, Fox’s time traveling thriller “Terra Nova” has hit more turbulance.

Exec producer David Fury has exited the prehistoric series due to creative differences. Fury had been sharing showrunning duties with Brannon Braga, who will continue as solo showrunner.

“Terra Nova,” from Twentieth Century Fox TV, is on tap to shoot in Australia next month. The ultra-ambitious project is targeting a May sneak preview and a fall 2011 debut.

The creative team has needed extra time to produce the show’s mega-concept: “Terra Nova” centers on people from the year 2149 who are forced to find a way to save the human race — and discover a rip in the time-space continuum that can send them back to pre-human Earth.

“Terra Nova” has been slow to find its cast; so far just Jason O’Mara and Allison Miller have signed on. Steven Spielberg and Peter Chernin are the exec producers behind “Terra Nova,” along with Braga. Show is also exec produced by Jon Cassar, Aaron Kaplan, Katherine Pope, Justin Falvey, Darryl Frank, Craig Silverstein and Kelly Marcel.