Scientists have discovered fossils of an ancient amphibian from the Late Triassic period in China that appears to have lived entirely in the ocean. The armored creature, which lived about 237 million years ago, challenges the long-held understanding that amphibians cannot survive permanently in saltwater. Researchers say the discovery in China provides the first convincing evidence of a fully marine amphibian in Earth’s evolutionary history.
The findings, published Oct. 26, 2026, in the journal Nature Ecology & Evolution, come from a study led by Lipin Diao. Researchers from Peking University, the University of California, Davis, and the Geological Museum of Guizhou examined two nearly complete fossil skeletons found in China’s Guizhou Province.
The newly identified species, named Gerrothorax maritimus, belonged to an extinct group of early amphibian relatives. Its unusual anatomy suggests it developed adaptations that allowed it to survive in conditions unsuitable for modern amphibians.
Ancient marine amphibian had armored body and unusual hunting style
The fossils reveal an animal with a broad, flattened body covered in thick bony armor. One specimen measured at least 74 centimeters (29 inches) long, giving the creature a body size comparable to a giant salamander. Unlike the long, narrow bodies of modern salamanders, however, Gerrothorax maritimus had a wide, disc-shaped appearance.
Researchers believe its armor may have offered protection against marine predators, including ichthyosaurs, ancient marine reptiles that inhabited the oceans during the Triassic period. The shape of the animal’s skull also provides clues about how it hunted. Scientists suggest it remained near the seafloor, waiting for smaller animals to approach before drawing them into its mouth through suction.
“They would probably just wait at the bottom and then when prey comes around, they would just suck it in,” said Ryosuke Motani, a professor at UC Davis and corresponding author of the study. Researchers compared this possible feeding behavior to that of modern wobbegong sharks, which hunt prey near the ocean floor.
Fossils provide evidence of life in the open ocean
The two skeletons came from marine deposits in Guizhou Province, an area covered by seawater during the Late Triassic. Researchers determined that the burial site lay at least 30 kilometers (19 miles) from possible islands, raising questions about how an amphibian could have reached such an environment.
The exceptional preservation of the fossils offered an important clue. Both skeletons retained delicate bones, including fingers, suggesting the animals died close to where their remains settled. Bodies carried long distances through seawater often lose smaller bones before reaching the seabed. The importance of well-preserved skeletons in reconstructing prehistoric marine life has also been demonstrated by the discovery of a rare Jurassic marine reptile in Britain.
Scientists also examined strontium isotopes preserved in the fossil bones. Their chemical signatures closely matched those of seawater from the same geological period. Together, the preserved skeletons, offshore location, and chemical evidence suggest the animals lived permanently in the sea rather than being washed there from freshwater habitats.
How did the ancient amphibian survive in saltwater?
More than 8,000 amphibian species live today, including frogs, salamanders, and caecilians. None live entirely in the ocean, and fewer than 2% show some degree of salt tolerance. Most amphibians have highly permeable skin that allows water and gases to pass through. Although useful for breathing and absorbing moisture, this makes it difficult to maintain the body’s water and salt balance in seawater.
Researchers believe Gerrothorax maritimus may have overcome this problem through its inherited body armor. The protective covering likely reduced direct water exchange through the skin, making the animal less dependent on the process used by modern amphibians. Instead, the creature may have relied on its gills and digestive system to manage salt and water.
Researchers suggest these organs could have allowed it to drink seawater and remove excess salt, making permanent marine life possible. However, the fossils cannot confirm exactly how these functions worked because the relevant soft tissues were not preserved.
Discovery changes understanding of amphibian evolution
The findings suggest that ancient amphibian relatives had a greater ability to adapt to different environments than previously recognized. While mammals, reptiles and birds have repeatedly evolved species capable of living entirely at sea, amphibians appeared to have remained restricted to freshwater and coastal habitats.
Other fossil discoveries have revealed unexpected details about life during the Triassic, including a 250-million-year-old embryo in South Africa that provided evidence about reproduction in early mammal ancestors.
Gerrothorax maritimus now provides evidence that at least one ancient amphibian lineage crossed the evolutionary barrier separating freshwater habitats from fully marine environments. Important questions remain, including how the species reproduced and regulated salt throughout its life.
Nevertheless, the discovery shows that anatomical features inherited from earlier ancestors may have helped amphibians occupy environments once considered beyond their biological limits. The research adds a previously unknown example of how land vertebrates returned to the oceans millions of years ago.
See all the latest news from Greece and the world at Greekreporter.com. Contact our newsroom to report an update or send your story, photos and videos. Follow GR on Google News and subscribe here to our daily email!
