Lowell Ganz and Babaloo Mandel??

In the trailer for this film when they show the credits famed comedy screenwriters Lowell Ganz and Babaloo Mandel are credited with the screenplay along with David Giler (who also has a "story by" credit).

In the film the only credited writer is David Giler. Does anyone know why Ganz and Mandel had their names removed from the film or their involvement as I'm a big fan of their work (and this movie)?