Researchers from the University of California Davis, Peking University, and the Geological Museum of Guizhou have discovered two nearly complete 237-million-year-old fossil skeletons in China's Guizhou Province, identifying them as Gerrothorax maritimus. This species represents the first fully marine amphibian on record, challenging the long-standing biological assumption that all amphibians are strictly dependent on freshwater due to their permeable skin. The findings were published in Nature Ecology & Evolution on October 26, 2026. The study's authors, including corresponding author Ryosuke Motani, emphasize that this discovery redefines our understanding of ancient marine ecosystems during the Late Triassic period. By analyzing deep-sea sediments and strontium isotope proportions that match Late Triassic seawater, the researchers confirmed the animal lived and died in a marine environment hundreds of miles from large landmasses, rather than being washed out to sea. To solve the paradox of how an amphibian could survive in salt water, the researchers propose that Gerrothorax maritimus utilized a unique combination of heavy bony armor to prevent skin absorption, combined with fish-like biology. The animal likely drank salt water through its mouth, processed it via its digestive tract, and relied on gills to filter out excess salt while hunting as a seafloor ambush predator. This groundbreaking paleontology discovery opens new avenues for exploring vertebrate adaptation and marine evolution. Scientists can apply these insights to re-evaluate other fossil records and understand how prehistoric organisms breached major physiological barriers to conquer diverse habitats during periods of severe ecological transition.
