Book excerpt: When Sci Hi's school for whiz kids is blasted 500 million years into the past, Paleontology class gets way more real and way more lethal. To jump forward through time, Sidney, Hari, and Penny must survive slimy trilobites, paleo sharks, and hungry dinos. Studying these weird prehistoric beasts is the chance of a hundred million lifetimes. But can Sidney and his friends find a way to return to their own time before whatever killed the dinosaurs annihilates them, too?