DreamWorks Animation (DWA) announced today that its chairman of the board, Roger Enrico, has stepped down, effectively immediately. Director Mellody Hobson has been named to replace him.

Enrico had been chairman since DreamWorks went public back in 2004, and had previously been chairman and CEO of PepsiCo (PEP -2.97%), where he spent 31 years. The company did not provide a reason in its press release for Enrico's departure. 

In a statement, CEO Jeffrey Katzenberg said, "Roger has been an invaluable leader to our Board of Directors and his guidance helped put DreamWorks Animation on a path to success from day one. On behalf of the Board of Directors and our entire management team, I'd like to deeply thank Roger for his unfailing service over the past eight years and wish him the very best in the future."

Hobson is president and a director of Ariel Capital Management, a Chicago-based investment management firm.

DreamWorks is set to report third-quarter results on Oct. 30.