The evolution of fish from having no jaws to having jaws was presented as a process for the first time in the Feb. 12, 2014, issue of the journal Nature by a team of French and Swedish researchers led by Vincent Dupret of Uppsala University in Sweden.
There are presently about 50,000 species of jawed vertebrates on Earth and only two jawless vertebrates.
The researchers tracked the turning point in the development of jaws to an armored fish called Romundina that lived 410 million years ago. The researchers used a specimen of Romundina originally discovered in Canada that was stored in the collections of the Muséum national d'Histoire naturelle of Paris.
Romundina had a short front end to the brain like jawless vertebrates but had two nostrils and no jaws like most modern vertebrates. Romundina was the first vertebrate to have all the necessary structures to form jaws and faces like the majority of vertebrates have today.
A comparison of Romundina with fish and other vertebrates that lived before and after Romundina did show that the development of a larger front brain produced the necessity for two nostrils and jaws. The evolution of jaws, brains, and faces was produced using x-ray analysis of the animal’s skulls at the European Synchrotron Radiation Facility in Grenoble, France