375 million years ago an aquatic animal took the first steps to populate the emerged lands. It was Tiktaalik roseae , a half-fish, half-tetrapod creature discovered only four years ago and identified as the "missing link" between aquatic and terrestrial animals.
Now new research on the fossil of this predator reveals that, to achieve the transition, there were complex changes in the skeleton that are not limited to changing the fins for legs . Among other things, Tiktaalik developed a neck , unnecessary for fish, as published today in the journal Nature . Furthermore, at ground level the head tended to flatten and the muzzle to lengthen . Finally, Tiktaalik experimented with the gradual reduction of a bone called the hyomandible, which in fish joins the skull with the palate and the scales, but in mammals, including humans, it has evolved to become part of the middle ear.
