National Geographic returns to the primeval world with two absorbing documentaries chronicling landmark dinosaur discoveries. In "Dino Autopsy," a 70-million-year-old dinosaur, the most intact mummified animal of its kind, is unearthed. "Dino Death Trap" explores a massive find in China's Gobi Desert -- a Jurassic-era graveyard full of the prehistoric creatures -- supporting the theory that catastrophic events caused their extinction.