When animals gave up the buoyancy of water to fight gravity and crawl about on land, it marked a major step in vertebrate evolution. Another significant victory came when they began to walk on two legs instead of four.
Now, scientists say that a newly described fossil of a 10-inch reptile pushes back the advent of terrestrial bipedalism by about 60 million years. The researchers, who report their find in the Nov. 3 Science, have dubbed the 290-million-year-old animal Eudibamus cursoris, which means primitive two-legged runner.
Evidence of bipedalism in the well-preserved fossil includes forelimbs that are much shorter than its hindli