Fossil Sheds Light on Jaw Evolution
A new paper in Nature by Simon Conway Morris and Jean-Bernard Caron redescribe a Cambrian vertebrate known as Metaspriggina, providing missing evidence for a critical stage in the evolution of the jaw.
The study is based on new and better preserved specimens from the Burgess Shale in British Columbia, dating to about 505 million years ago. They show that Metaspriggina had 7 pairs of external gill bars. More importantly, the anterior most pair were larger and not associated with an actual gill. It’s possible that this anterior pair of gill bars would later become jaws.
This represents evidence for a critical step in the evolution of jawed vertebrates. Scientists predicted such a creature should exist, and now it has been found.
Everyone said it should have existed, but it’s never been found,” Morris said. “It looks remarkably like the hypothetical animal that we’d talked about.”