Oedipus Rex or was not was--everybody do the dinosaur!

The Sphinx challenged Oedipus on the road to Thebes with a riddle: what creature walks on four legs, then two, then three? Paleontologists have found themselves confronted puzzle, as New Scientist reports, and this is really mind-blowing and disabusing. Certain specimens that researchers have always held to be examples of different species may actually be the same animal at different stages of growth and development. If people did not have the experience of frogs and butterflies contemporarily, who would have thought to connect them to fossil evidence of tadpoles or caterpillars?