Little Critter's class is going to the Critterville Museum of Natural History and everyone is excited. But when the class arrives, they find out the dinosaur exhibit is closed because of a missing Triceratops bone. Little Critter searches the Hall of Minerals and sneaks around the Planetarium to solve the mystery of the lost dinosaur bone. Author - Mayer, Mercer Illustrator - Mayer, Mercer Number of Pages - 24 Format - Paperback Publisher - HarperCollins Published - 2007-11-20