Broken leg bone reveals switch to life on land

摘要

It was one small fall for a tetrapod, but It signals one giant leap for tetrapod kind. A broken leg bone pushes back the emergence of our four-legged ancestors from water on to land by at least 2 million years. A gap in the tetrapod fossil record means we know little about what happened between the time when limbs evolved from fish fins some 360 million years ago and the first land-adapted tetrapods appeared 330 million years ago.