Researchers at the Australian National University and Queensland Museum have used CT scan technology to digitally dissect the jaws of a fossil of Buchanosteus – an armoured fish from the extinct placoderm group – found about 50 kilometres from Canberra.

The researchers created three-dimensional prints of the fossil's jaws to find out how the jaws moved and whether the fish had teeth, which could help determine a key stage in the evolution of teeth.

ANU palaeontologist Dr Gavin Young said the CT scans were to investigate the internal structure of the fragile fossil skulls and braincases from acid-etched limestone.

"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," he said.

Co-researcher Yuzhi Hu said the evolutionary origin of teeth remained one of the great scientific questions.

Queensland Museum's Dr Carole Burrow said placoderms were a common focus in "the question of tooth origins".

"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," she said.

Findings from the Australian Research Council-funded work were published this week in Biology Letters, disputing the findings of a study published last year that suggested placoderms had "real teeth".