Paleontologists have described Gerrothorax maritimus, which they say is the first known fully marine species of stalked amphibian. The species lived in the Late Triassic seas of what is now China about 237 million years ago, and is known from two nearly complete skeletons found in Guizhou province.
There are currently more than 8,000 amphibian species, but none of them live in the ocean. Frogs, salamanders and their relatives generally depend on freshwater, and fewer than 2% of amphibian species show any degree of tolerance to salinity.
Mammals, reptiles and birds have all evolved lineages that returned to the ocean, making amphibians notable exceptions. Gerrothorax maritimus may be the first amphibian known to have lived without access to land or freshwater.
A heavily armored marine amphibian
The animal lived during the Late Triassic, about 237 million years ago. It was 73.7 centimeters (29 inches) long and had a flat, heavily armored body. That armor may have reduced water loss, while its gills and digestive system may have helped it manage salinity and swallow seawater.
“When you think about today’s amphibians, this animal is unusual because of its large size,” says Ryosuke Motani, a paleontologist at the University of California, Davis.
“It’s probably about the same as the giant salamander in terms of weight, but the difference is that the giant salamander is elongated, whereas this animal is very stocky.”
Bottom-dwelling suction feeder
Professor Motani and his colleagues hypothesize that Gerrothorax maritimus was a bottom-dwelling suction feeder.
“They probably waited on the bottom and just sucked up their prey when it approached,” Professor Motani says.
“This feeding style is similar to the modern benthic carpet shark, the wobbegong.”
Evidence of a fully marine lifestyle
The two specimens were discovered in rock in China’s Guizhou province, dozens of kilometers from any large landmass. Their strontium isotope signatures matched what would be expected from Late Triassic seawater.
“The distinct occurrence of Gerrothorax maritimus far from land, together with the associated strontium isotope record, suggests life in a fully oceanic regime,” the authors said.
“It descended from a lineage with complete body armor, which restricted the skin-based exchange of water, gases or salts typical of amphibians and instead forced the use of gills and guts that could increase salt tolerance. This likely prepared it for marine adaptation.”
The paper was published online on October 26, 2026, in Nature Ecology & Evolution.
Diao, L. et al. “A completely marine stalked amphibian that lived during the Late Triassic period of China.” Nature Ecology & Evolution, published online October 26, 2026. doi: 10.1038/s41559-026-03209-9.
Source: www.sci.news