Ancient Fish is Earliest Known Species With a Modern Jaw
Posted on September 29, 2013
The fossil of Entelognathus primordialis, a previously unknown armor-plated fish, has been found in China. The fish, which lived 419 million years ago, had a modern-like bony jaw and a turtle-like face. You could be staring at an image of one of your ancient ancestors right now.
The L.A. Times explains explains why the finding is extremely significant. Scientists think the modern jaw evolved from a group of bony-plated fishes, known as osteichthyans. Osteichthyans are thought to hvae evolved from from a shark-like ancestor while the placoderms, an extinct class of ancient armored fish, died out. E. primordialis and its bony face suggest this may not be the case as it is older than both sharks and osteichthyans.
Nature reports that the discovery could mean sharks are less primitive than previously thought. It is also possible the previous jaw evolution theory is correct and that the jaw of the newly discovered ancient fish evolved its jawline independently from bony-plated fishes.
The Smithsonian blog sums up the finding by saying, "In other words, this fossil might mean that the placoderms didn't go extinct, but rather evolved into the tremendous diversity of animals that live on both land and sea - and that this ancient, strange-looking face belongs to one of your oldest ancestors."
The discovery, "A Silurian placoderm with osteichthyan-like marginal jaw bones," was reported here in Nature.