Australasian Science: Australia's authority on science since 1938

Little Gap in Tooth Evolution

By Stephen Luntz

Teeth may have evolved earlier than previously recognised following the latest discovery from the rich Devonian fossil site at Gogo in the Kimberleys.

Dr Kate Trinajstic of Curtin University’s Department of Chemistry was part of an international team that revealed in Nature their use of synchrotron light to examine the jaw of Compagopiscis, an early placoderm fish. Compagopiscis was a relatively early jawed fish, so the team’s discovery of tooth remnants indicates that there was little gap between the evolution of the jaw and teeth.

“It was a great achievement to finally solve the debate on the origins of teeth,” says Trinajstic. “We’ve always known exceptionally preserved fossils, such as those from Western Australia, hold a lot of answers to many evolutionary questions, but research like this has been waiting for non-destructive technology to study fossils without touching them.”

Serrations in the jaw were known prior to the synchrotron work, but Trinajstic says: “They appeared to be continuous with the jaw, so we were not sure if they were true teeth or a jawbone with serrations.”

X-rays revealed that the teeth were made up of dentine over a pulp canal, which filled with bone as the fish aged. Consequently, they were not able to replace worn or lost teeth like modern sharks can.

The teeth would have proved an enormous advantage in the Devonian oceans. “As soon as you have jaws and teeth, by definition you can become the top predator,” says Trinajstic.

Although the discovery shortens the gap between the evolution of jaws and teeth, Trinajstic does not believe that the two evolved simultaneously, saying that some of the more primitive placoderms do not appear to have had teeth.

“We think that scales on the body of the fish migrated to the mouth, and the first teeth were actually equivalent to body scales,” Trinajstic says. “This is the simplest explanation.”