No one knows exactly how dinosaurian dominance came to an end. Paleontologists and geologists have identified the triggers for the end-Cretaceous mass extinction that devastated life on Earth 66 million years ago, yet, even with that knowledge, we still lack the resolution to comprehend how asteroid impact, volcanic activity, and climate change conspired to snuff out so many species while sparing others. Truly understanding a mass extinction goes deeper than pinning down ultimate causes of catastrophe. In fact, paleontologists still have a great deal of work to do in the effort to catalog who was around when the terminal-Mesozoic calamity struck, and the latest clue from the roll of victims is a succession of non-avian dinosaur tracks found among the