A dinosaur relative about the size of an iguana, which lived at the bottom of the world 250 million years ago, is throwing paleontologists for a loop. Antarctanax shackletoni, named for explorer Ernest Shackleton, hints at unexpected biodiversity on the now-frozen continent of Antarctica.

About 252 million years ago, the greatest mass extinction known walloped life on Earth. An estimated 90 percent of all living things perished. In the wake of this event, known as the end-Permian or Gre