BEIJING, 27 October 2026 — Researchers have identified the first amphibian known to have lived its entire life in the sea: a flat, armoured, bottom-dwelling creature that swam in the oceans of what is now southern China about 237 million years ago, during the Triassic Period. The discovery, reported by Reuters on 27 October 2026, rewrites a long-standing rule of amphibian biology — that no amphibian, living or extinct, could make a full-time home in salt water.
The creature, named Gerrothorax maritimus, is described in a study published in the journal Nature Ecology & Evolution, based on two nearly complete skeletons unearthed in Guizhou Province. About 75 centimetres (30 inches) long, it had a flat, disc-shaped, bony-armoured body and a wide mouth lined with many small, conical teeth — the anatomy of an ambush predator that waited on the sea floor and sucked passing prey into its mouth.
Illustration: The fossil skeleton of Gerrothorax maritimus, the first amphibian known to have lived full-time in the sea.
What Happened
Amphibians — the group that includes frogs, salamanders and caecilians — rely on their permeable skin for breathing and drinking, a trait that works well in fresh water but is undermined by the salt in seawater. Salt draws water out of a permeable body, making a marine life difficult or impossible. As a result, scientists had never found an amphibian, extinct or living, with a fully marine lifestyle — until now.
"The most important finding is that there was an early amphibian that lived in the sea full-time," said paleobiologist Ryosuke Motani of the University of California, Davis, one of the leaders of the study, according to Reuters. The fossils were found in rocks that formed from ocean sediment, a key line of evidence for a marine habitat, and they were discovered near fossils of an ichthyosaur — a marine reptile called Guizhouichthyosaurus that measured about seven metres (23 feet) long and was among the apex predators of its seas.
The animal's body plan tells the story of its life. "The skull is flat and wide with a large mouth, having many small conical teeth," said paleontologist and study co-author Da-yong Jiang of Peking University, according to Reuters. "It is a bottom animal, a suction feeder that lived on a muddy to silty seafloor. It would likely capture anything that swam by, such as fish, worms and maybe cephalopods," Jiang said, referring to squid relatives.
Background
Gerrothorax maritimus lived during the Triassic Period, which began about 252 million years ago in the aftermath of the greatest mass extinction in Earth's history, the end-Permian event. Life was rebuilding itself, and the oceans were being recolonised by new groups of predators and prey. The Triassic seas of southern China, preserved today in the rocks of Guizhou Province, are among the richest fossil windows into that recovery, yielding ichthyosaurs, early marine reptiles and a diverse cast of fishes and invertebrates.
The creature predated the dinosaurs, which were only beginning to emerge during the Triassic. Its relatives belonged to an ancient branch of amphibians that were far more diverse in body form than the frogs and salamanders familiar today. Some were large, crocodile-like predators of rivers and lakes; Gerrothorax shows that at least one lineage pushed further, out of fresh water and into the sea itself.
The discovery also highlights why Guizhou has become one of the world's most important fossil regions. Its marine sediments preserve not just isolated bones but, in this case, two nearly complete skeletons — a rarity that allowed researchers to reconstruct the animal's body shape, feeding style and habitat with unusual confidence. The presence of the giant ichthyosaur nearby confirms the setting: these were open marine sediments, not a river mouth or a brackish lagoon where a freshwater animal might occasionally stray.
Illustration: Gerrothorax maritimus resting on a Triassic sea floor, waiting to ambush passing prey.
For decades, textbooks have treated the amphibian story as a freshwater story: amphibians evolved from lobe-finned fishes, colonised the land, and stayed tied to moist, freshwater environments because of their permeable skin. Modern amphibians follow the same pattern — no frog, salamander or caecilian lives in the open ocean, although a few tolerate brackish water at the edges of mangroves and estuaries. A fully marine amphibian was, until now, a gap in the fossil record that many assumed reflected a genuine biological limit.
Gerrothorax maritimus does not overturn the physiology — its skin was presumably still permeable — but it shows that an early amphibian found a way to live with that constraint in the sea, perhaps through behaviour, habitat choice on the sea floor, or physiological adaptations that the bones alone cannot reveal. Researchers will now look for clues in related fossils and in the chemistry of the surrounding rocks to understand how it managed the salt problem.
Why It Matters
First, the fossil breaks a rule. Science advances not only by confirming expectations but by finding the exception that forces a rethink, and a fully marine amphibian is exactly that kind of exception. It tells researchers that the ecological range of early amphibians was wider than assumed, and that the absence of marine amphibians today is a product of later history — extinction, competition and changing seas — rather than an absolute biological impossibility.
Second, it enriches the picture of Triassic recovery. After the end-Permian extinction wiped out much of marine life, the Triassic oceans were rebuilt by survivors and newcomers. Finding an amphibian among the marine predators and prey of Guizhou shows that the recovery drew on unexpected groups, and that the boundary between freshwater and marine ecosystems was more porous in the deep past than it is today.
Third, the discovery is a reminder of how much remains hidden in the fossil record. Two nearly complete skeletons were enough to rewrite a chapter of amphibian history, yet they sat in rocks that have been studied for decades. As new sites are explored and old collections re-examined with modern techniques, similar surprises are likely — and each one refines our understanding of how life adapts to extreme environments.
Finally, there is a conservation resonance. Modern amphibians are among the most threatened groups of animals on Earth, facing habitat loss, disease, pollution and climate change. Their deep history shows a group that was once far more ecologically adventurous than its surviving members suggest. Understanding that history does not save a single frog, but it deepens the case for protecting a lineage whose story stretches back hundreds of millions of years and once reached, remarkably, into the sea itself.
What Happens Next
The research team and other paleontologists are expected to examine the Guizhou material in greater detail, comparing Gerrothorax maritimus with related amphibians to pin down its place in the amphibian family tree and to test how its marine lifestyle evolved. Chemical analysis of the fossils and surrounding sediments may shed light on the salinity of its habitat and on whether it spent its whole life at sea or moved between environments.
Illustration: Paleontologists at work in Guizhou Province, whose marine rocks preserve a remarkable Triassic fossil record.
Fieldwork in Guizhou will also continue. The province's Triassic marine deposits have yielded new species regularly, and researchers hope further specimens of Gerrothorax — juveniles, for example, or individuals preserved in different settings — could reveal how the animal grew, reproduced and coped with salt water. Each additional fossil would sharpen a picture that currently rests on two skeletons.
For the wider public, the discovery is likely to feature in museum displays and popular accounts of prehistoric life, where a flat, armoured, sea-dwelling amphibian makes a memorable addition to the cast of Triassic creatures. It joins the ichthyosaurs and early marine reptiles as evidence of an ocean world in recovery — strange, diverse and far less familiar than the dinosaur-dominated landscapes that came later.
And for scientists, the find poses a new question to answer: if one amphibian conquered the sea 237 million years ago, why did none ever do so again? The search for that answer — in physiology, ecology and extinction — is now part of the research agenda that Gerrothorax maritimus has opened.
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FAQ
What is Gerrothorax maritimus?
It is a newly identified extinct amphibian from the Triassic Period, about 237 million years ago, described from two nearly complete skeletons found in Guizhou Province, China. About 75 centimetres long, it had a flat, disc-shaped, armoured body and a wide mouth suited to suction feeding on the sea floor.
Why is it called the first seagoing amphibian?
Before this discovery, no amphibian — extinct or living — was known to have lived full-time in the sea, because amphibians' permeable skin is poorly suited to salt water. The fossils were found in marine sediments alongside a giant ichthyosaur, indicating a fully marine lifestyle.
How did it catch its food?
It was a bottom-dwelling suction feeder. By rapidly expanding its mouth cavity, it created a pressure drop that drew water and prey — likely fish, worms and possibly cephalopods — into its wide mouth, according to co-author Da-yong Jiang of Peking University.
How old is the fossil, and where was it found?
The fossils are about 237 million years old, from the Triassic Period, and were unearthed in Guizhou Province in southern China, a region famous for its rich marine fossil deposits from that era.
Did it live alongside dinosaurs?
No — it predated the dinosaurs, which were only beginning to emerge during the Triassic. Its neighbours included the giant marine reptile Guizhouichthyosaurus, about seven metres long, which was among the apex predators of its seas.
Sources
- Reuters, "Ancient armored bottom-feeder is first seagoing amphibian," 27 October 2026.
- Study published in Nature Ecology & Evolution (2026), via Reuters reporting, 27 October 2026.
- Quotes from Ryosuke Motani, University of California, Davis, and Da-yong Jiang, Peking University, via Reuters, 27 October 2026.
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