Watch Dinosaurs Decoded (2009) Official Trailer

New evidence has paleontologists questioning whether a third of all dinosaur species ever existed. Could some discoveries once thought to be distinct species, in fact, be the same species at different stages of development? National Geographic joins famed paleontologists—including Jack Horner, a contributing expert to the Jurassic Park films—who are challenging the long held belief that young dinosaurs looked like miniature versions of their parents.