All vertebrates have their evolutionary roots in fishes.
But although countless fossil fishes have been found, their shared family tree still features many gaps. Now, British and Chinese researchers think they can add another piece to the evolutionary puzzle. Shark's forebears had already left the common family tree to form their own branch millions of years ago. The researchers now speculate that early fishes may have shared common traits longer than previously thought. Possibly, the specialization of the various species was less marked than previously thought.