Researchers find evidence of ancient amphibians living at sea

Two amphibian fossils from China suggest the animals lived at sea 237 million years ago, researchers argue in a study published in Nature Ecology & Evolution on October 26, 2026. None of the more than 8,000 modern amphibian species lives exclusively in a marine environment.

The fossils came from present-day Guizhou province, an area covered by a salty sea during the Late Triassic period. The animals belonged to an ancient amphibian group called temnospondyls. Provisionally named Gerrothorax maritimus, the species was about 74 centimetres long, with a flattened body almost completely covered in armour.

Analysis

Why the researchers point to seawater

Study co-author Ryosuke Motani, a palaeobiologist at the University of California, Davis, told Nature that amphibians vary in their tolerance of salt. Even salt-tolerant animals need to recover from excess salt, usually by drinking fresh water.

The researchers argue that fresh water was not an option for these animals. The skeletons were exceptionally well preserved and lay far from any land mass that existed at the time. Together, those features suggest the animals were not simply washed out to sea, the team says.

The team also measured strontium isotopes—different forms of the same element—in the bones. The measurements matched seawater from that time. The researchers interpret that match as evidence that the animals grew up drinking seawater, rather than relying on fresh water.

Steve Brusatte, a palaeontologist and evolutionary biologist at the University of Edinburgh, called the discovery potentially revolutionary. His assessment depended on whether the amphibian really lived entirely at sea: