The newly discovered amphibian species Gerrothorax maritimus was approximately 74 centimetres long and had a flat, armoured body.Credit: Ryosuke Motani
A newly reported fossil suggests that amphibians may have lived in the sea 237 million years ago, during the Late Triassic period. The two exceptionally well-preserved fossils, discovered in what is now China’s Guizhou province, belong to a primitive amphibian group called temnospondyls. Researchers have tentatively named the species Gerrothorax maritimus.
The finding, reported in Nature Ecology & Evolution1, could challenge the view that amphibians have never adapted to live exclusively in marine environments. The approximately 74-centimetre-long animal had a flat body that was almost completely covered by armour.
More than 8,000 amphibian species are alive today, but none lives exclusively in the marine environment. “This is a potentially revolutionary discovery,” says Steve Brusatte, a palaeontologist and evolutionary biologist at the University of Edinburgh in the UK. “This Triassic amphibian would be a game changer if it were truly fully oceanic.”
A schematic diagram of one of the amphibian fossils, with the bones labelled and colour-coded according to skeletal parts.Credit: Diao, L. et al./Nature Ecology & Evolution
Evidence of life in seawater
Amphibians have different levels of tolerance to salt, says Ryosuke Motani, a palaeontologist at the University of California, Davis, and a co-author of the study. Even salt-tolerant animals must find a way to eliminate excess salt, he explains. “Most of the time they do it by drinking fresh water.”
According to the researchers, that would not have been an option for G. maritimus. The skeletons are exceptionally well preserved and were found far from any land that existed at the time, suggesting that the animals were not washed out to sea by freshwater or coastal waters.
The researchers also measured isotopes of strontium, an element that can be used to compare minerals and water with ocean samples. The levels in the ancient animal’s bones match those of seawater from the period, suggesting that the amphibian “fed on seawater”, the researchers wrote in their paper.
Source: www.nature.com
