A freaky fish with a head like a dolphin and a body like a tank may be to thank for human jaws.
The discovery of fish from China suggests that the jaws of all modern land vertebrates and bony fish originated in a bizarre group of animals called placoderms, researchers report in the Oct. 21 Science.
John Long, a paleontologist at Flinders University in Australia, says the 423-million-year-old discovery “fills a big gap in our understanding of how vertebrate jaws evolved.”
Researchers say the origin of human jaws is a complicated topic. Modern vertebrates, including humans, have a jaw that is made up of three parts: the dentary, maxilla and premaxilla.
Historically, only the now extinct placoderms have been discovered to have similar jaw bones, which have long been thought of as unrelated to human jaws, however. That began to change several years ago when researchers unveiled a bony fish fossil called Entelognathus, whose body resembles that of a placoderm and also a three-part jaw, in Yunnan. The placoderm-like traits in the early fish fossil began building a strong case that a close relationship existed between bony fish and placoderms.
Now, the Qilinyu, which has been discovered in the same place and time period as Entelognathus, is strengthening that argument. With an estimated total body length exceeding 20 centimeters, the Qilinyu has skeletons that combine placoderm skeletons with the dentary, maxilla and premaxilla. These discoveries suggest that human jaw bones may have evolved from those of placoderms.
According to Long, evolutionary biologists have long discounted placoderms in their research, but now the new findings in Yunan will change that as they realize the importance of these prehistoric creatures in helping to understand “the early assembly of the vertebrate body plan.”