Guizhou museum team identifies first fully marine basal amphibian

An international research team involving the Geological Museum of Guizhou, Peking University, and the University of California, Davis, has identified a new amphibian species that lived about 237 million years ago, based on two nearly complete fossil skeletons discovered in Late Triassic strata in Guanling county, Guizhou province.

The animal had a flattened body, heavy bony armor, a broad head, a wide mouth, and well-developed gill arches. According to Jiang Dayong, a professor at Peking University and co-corresponding author of the study, it is the first known basal amphibian capable of living entirely in a marine environment.

Its flattened body likely helped it hide in seafloor sediments, while its armor may have reduced water loss through the skin. Adults retained gills and may have breathed underwater without surfacing. With its wide mouth and strong gill arches, the animal likely sucked in small fish as an ambush predator, much like modern carpet sharks.

To confirm its marine habitat, researchers analyzed strontium isotope ratios in the fossils and surrounding rock. The bones retained the isotopic signature of seawater from that period, supporting the conclusion that the animal lived in the ocean before burial. The fossils' exceptional completeness and the site's ancient geography provided further evidence.