Screenwriter Michael Arndt is exiting Star Wars: Episode VII with director J.J. Abrams and Lawrence Kasdan assuming scripting duties.

Lucasfilm made the unexpected announcement Thursday. Kasdan co-wrote The Empire Strikes Back and Return of the Jedi, making him a revered figured in Star Wars lore. The 64-year-old scribe, who also wrote Raiders of the Lost Ark, had been serving as a consultant on the film.

Film-Star Wars Screenwriter

Michael Arndt poses with the Oscar he won for best original screenplay for his work on Little Miss Sunshine. Arndt is exiting Star Wars: Episode VII with director J.J. Abrams and Lawrence Kasdan assuming scripting duties. (Kevork Djansezian/Associated Press)

"There are few people who fundamentally understand the way a Star Wars story works like Larry," Lucasfilm President Kathleen Kennedy said in a statement. "Michael Arndt has done a terrific job bringing us to this point."

Arndt was named the sole screenwriter last year. He won an Oscar for the script to Little Miss Sunshine, and also wrote Toy Story 3 and The Hunger Games: Catching Fire.

Shooting for Star Wars: Episode VII is to start in the spring, with the film due out in 2015.