Triassic armored amphibian Gerrothorax maritimus lived fully marine, study shows

A study published Monday in Nature Ecology & Evolution reveals that the late Triassic amphibian Gerrothorax maritimus was a rare fully marine species. The researchers examined the chemical signatures of two nearly complete skeletons uncovered in Guizhou Province, China, and found evidence that the animal could endure continuous exposure to seawater, unlike modern amphibians whose permeable skin cannot handle salt. Measuring under two feet in length, the creature was encased in a sturdy armor that likely helped retain internal fluids and protect it from predators, including the giant ichthyosaur Guizhouichthyosaurus whose remains were found in the same rock layer.

Its gills allowed it to extract oxygen underwater, enabling a seafloor-dwelling lifestyle. The fossils, originally gathered by local farmers in 2004, are now exhibited at a geological museum in Guiyang. Lead authors Ryosuke Motani of the University of California, Davis, and Dayong Jiang of Beijing highlight that this lineage left no modern descendants, yet the discovery expands understanding of amphibian evolutionary diversity.