Armoured and at home in the ocean: the amphibian that lived its whole life at sea, 237 million years ago

No amphibian alive today — out of more than 8,000 species — can live in the sea; salt water is supposed to be beyond them. Two beautifully preserved fossils from Guizhou province in China tell a different story about the deep past. The creature, provisionally named Gerrothorax maritimus, was a 74-centimetre, flattened amphibian almost completely covered in body armour, and it lived 237 million years ago in a salty Triassic sea, hundreds of miles from any land. Chemical fingerprints in its bones match the ancient seawater around it, showing it grew up drinking the ocean itself — making it the first fully marine amphibian ever found, in research published today in Nature Ecology & Evolution. Outside experts call it a potential game-changer for understanding how the first four-limbed animals lived.