Eridahn — Robert F. Young

In 1998, Jim Carpenter drove a time machine for a living, and his last job seemed simple enough: go back in time 74 million years and find out how a human skeleton got mixed up with dinosaur bones -- millions of years before that could possibly happen! But then Jim found two frightened, well-dressed kids hiding from a dinosaur. They claimed to be the prince and princess of Mars! Well, the boy claimed they were. The girl, it seemed, didn't speak to commoners . . .