Lungfish have kept same pattern of tooth development for 360 million years

Lungfish - the closest living relatives of four-limbed animals - have maintained the same pattern of tooth development throughout 360 million years of evolution, according to a report in this week's Nature.

Moreover, this pattern is unique to lungfish, suggesting that it evolved within this group and became the only possible pattern for its modern descendants.

Moya Smith of Kings College, London, and Robert Reisz of the University of Toronto, examined the tooth development of Neoceratodus, a modern lungfish that occurs in Australia.

They compared it to a series of fossils of Andreyevichthys, an extinct species from the Late Devonian period. These fossils, found in central Russia, are the only known example showing all the stages from hatchling to adult.

The tooth development pattern in lungfish is unique.

Nature

Modern adult lungfish have 'tooth plates' on the palate and lower jaw, which, unlike in humans, are formed by addition of new teeth without losing previous ones.

This process could also be seen in the fossil series.

In addition, hatchlings have a separate set of teeth further forward that are lost by the juvenile stage, starting with the single middle tooth.

This was again seen in the fossil series - hatchling fossils possessed these teeth, but juvenile and adult fossils did not.