Paleontologists have described Gerrothorax maritimus, which they claim is the first known completely marine stalked amphibian. The species is based on two nearly complete skeletons discovered in Late Triassic rocks in China, and may represent the first amphibian known to have lived without access to land or freshwater.
More than 8,000 amphibian species live today, but none is known to inhabit the open ocean. Frogs, salamanders and their relatives generally depend on freshwater, and fewer than 2% of living amphibian species show any degree of tolerance to salinity.
Mammals, reptiles and birds have all evolved lineages that returned to the ocean, making amphibians unusual among major vertebrate groups in having no fully marine living representatives.
A heavily armored marine amphibian
Gerrothorax maritimus lived in what is now China during the Late Triassic, about 237 million years ago. It reached 73.7 centimeters (29 inches) in length and had a flat, heavily armored body. The armor may have reduced water loss, while the animal’s 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.”
The two specimens were discovered in rocks in China’s Guizhou province, dozens of kilometers from any large landmass. Their strontium isotope signatures matched those expected from Late Triassic seawater.
“The distinct occurrence 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 study was published online on October 26, 2026, in Nature Ecology & Evolution.
L. Diao 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
