Ancient fish may have set stage for jaws
New fossils reveal gills possibly on their way to chomping on prey
One of the earliest outlines of jaws may have been written in the gills of a fish called Metaspriggina walcotti.
The fish, which lived roughly 500 million years ago, had been described previously. But 100 new specimens collected in the Canadian Rockies provide a detailed look at the creature’s gill bars, the structures that ran vertically down the body and supported the gills. In M. walcotti, each gill bar had an upper and lower arch, possibly made of cartilage-like tissue. The front set of gill bars was slightly thicker than the others and did not actually have gills beside them. These gill bars might have served as a precursor to the jaws that evolved around 420 million years ago in younger fish, researchers argue June 11 in Nature.