ACTON, Australia, Sept. 30 (UPI) -- Scientists believe a 400 million-year-old fish fossil holds clues to the evolutionary origins of human teeth.

Upon excavation, it wasn't clear whether the ancient armored fish had jaws or teeth. But CT scans allowed scientists to create a 3D-printed model of the fossil, revealing both a jaw and teeth.


How and when teeth first appeared on the evolutionary timeline remains an unanswered question for biologists. Buchanosteus, from the extinct placoderm group, may offer answers.

"We are conducting further research on the internal tissue structure of tooth-like denticles in the mouth of the fish fossil, to determine whether they represent a transitional stage in the evolution of teeth," Gavin Young, a researcher at Australian National University, said in a news release.

Previous research has suggested extinct placoderms possessed "real teeth" or "true teeth," a more evolved iteration. But the latest findings -- detailed in the journal Biology Letters -- undermine such a hypothesis, suggesting instead that the group of armored fish possessed a more primitive form of teeth.

"It's great that we are able to use recent technology, such as micro-CT scanning and 3D printing, to examine some of the earliest known evidence of tooth-like structures in the most primitive jawed fishes," said Carole Burrow, a scientist from the Queensland Museum.

"Placoderms have been a common focus in the question of tooth origins," Burrow added. "Our team has been able to examine the gnathal plates of placoderms from the Early Devonian period, and compare their internal and external structure with those of younger placoderms as well as with the true teeth in other jawed fishes."