Ecology: Armoured amphibian adapted to life at sea (Nature Ecology & Evolution)
27 October 2026
A newly identified fossil amphibian, measuring 737 millimetres in length and dating back around 237 million years, may have been fully adapted to life in the sea, according to a study published in Nature Ecology & Evolution. The species, named Gerrothorax maritimus, could be the first known amphibian to have lived without access to land or fresh water. Although no amphibian lives entirely at sea today, the findings suggest that amphibian evolution once found a way across this ecological barrier to make a fully marine lifestyle possible.
More than 8,000 amphibian species live today, including frogs, salamanders, and caecilians, but none is strictly marine. Their permeable skin helps them to breathe, but can also cause water loss in the sea, where high salt levels create further physiological challenges. Some living amphibians tolerate brackish habitats, where fresh water and seawater mix, and fossils of older species have been found in coastal deposits. However, previous evidence has not established a fully marine lifestyle.
Ryosuke Motani and colleagues examined two nearly complete skeletons discovered in Late Triassic rocks in Guizhou Province, China with a minimum length of 737 millimetres. The animals were buried at least 30 kilometres from possible islands, and their preservation suggests that they died near this location. Analysis of chemical signatures of the bones closely matched that of seawater at the time. Together, this evidence suggests that the animals lived and died in a marine environment.
The species had a flattened, heavily armoured body that may have reduced water loss, while its gills and digestive system may have helped it manage salt and swallowed seawater. The fossil’s mouth shape also indicates that G. maritimus may have fed by drawing prey into its mouth from the seabed. However, soft tissues were not preserved, so aspects of its physiology and reproduction remain unknown.
The discovery expands our understanding of amphibian evolution, suggesting that even a group now absent from the oceans used body armour and aquatic adaptations to support a fully marine lifestyle.
- Article
- Published: 26 October 2026
Diao, L., Motani, R., Jiang, Dy. et al. A fully marine stem amphibian from the Late Triassic of China. Nat Ecol Evol (2026). https://doi.org/10.1038/s41559-026-03209-9
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