This is certainly not just another fish tale. A tiny jawless fish that lived more than a half-billion years ago is providing scientists with a treasure-trove of information about the very dawn of vertebrate life on Earth.

Researchers on Wednesday described about 100 fossil specimens of the fish unearthed at the Burgess Shale site in the Canadian Rockies and other locales, many exquisitely preserved and showing the primitive body structures that would later evolve into jaws.

The fish, Metaspriggina, lived about 515 million to 500 million years ago amid the astonishing flourishing of complex life during the Cambrian Period. While two fragmentary specimens had been found previously, the new ones revealed unprecedented detail about one of the earliest known vertebrates.