These days, most of the fish you find in Wisconsin’s lakes and elsewhere have jaws. But in ancient times, most fish were jawless and sucked up their prey through their mouths. It was not until 420 million years ago, during the Devonian period, that fish jaws evolved.
Today, the only types of jawless fish that exist are lampreys and hagfish. Scientists used to believe that jawed fish had the ability to prey on more species than did the jawless fish, thus leading to the eventual extinction of jawless fish.
According to new research published in the journal Nature, however, this could not have happened. And these two types of jawless fish survived for 10 million years.
“If they couldn’t compete, they probably should have gone out when the jawed fish reached their functional peak,” said Dr. Philip Anderson, the study’s lead author, an evolutionary paleobiologist at the University of Bristol in England.
After examining fossils throughout the world, Anderson and his co-authors have developed a knowledge-based understanding of the appearance of jaws in fish. The first distinct jaws emerged 10 million years ago. Anderson said, “There were slender jaws with sharp, pointy teeth, good for quickly snapping at evasive prey, and [there were] jaws with big, blunt plates, thick and robust and probably more powerful.”
As more fish species evolved with jaws, they could do more than suck up their prey. They could grab and chew their meals. It is possible that the jawed fish were not searching for the same resources as other species. According to Anderson, the other jawless fish species died out from a different, yet-unknown, cause.
[Sources: The New York Times; Nature]