First amphibian discovered: it lived 237 million years ago.

Fossil remains of the first amphibian adapted to live exclusively in a marine environment have been discovered in China. The animal, named Gerrothorax maritimus, lived 237 million years ago, in the Upper Triassic, and reached a length of nearly 90 centimeters.

Researchers from the University of California at Davis, Peking University, and the Guizhou Geological Museum analyzed two nearly complete skeletons found in an area that was then covered by the ocean. The amphibian had a flattened, disc-shaped body and was covered in bony armor that protected it from predators and allowed it to tolerate salinity.

According to paleontologists, the animal likely spent most of its time on the seabed waiting for prey, which it would suck in as they approached. The discovery, documented in the journal Nature Ecology & Evolution, was made possible by the exceptional preservation state of the fossils.

Today's amphibians, such as frogs and salamanders, cannot survive in the sea because their skin cannot tolerate the salinity of the water. This discovery, however, shows that in the distant past, some amphibians developed unique adaptations to colonize marine environments.

Gerrothorax maritimus lived during the Triassic period, a geological era that began about 252 million years ago and was characterized by the recovery of life after the largest mass extinction in Earth's history. During this period, many animal groups diversified, exploring new ecological niches.

The key adaptation of this amphibian was its bony armor, which prevented the absorption of saltwater through the skin. To hydrate, it had to drink seawater through its mouth and absorb it through the digestive system, while its gills allowed it to filter and eliminate salt. This represents an evolutionary solution radically different from that of modern amphibians.