Fossil shows an amphibian that lived fully in the Triassic sea

Overview

Updated 1 hour ago

No living amphibian spends its life in the sea. Of the more than 8,000 modern species, all handle saltwater in short bursts with freshwater breaks—none is fully marine. A paper published today in Nature Ecology & Evolution reports a 237-million-year-old amphibian that grew up drinking seawater, overturning that picture.

The fossil, Gerrothorax maritimus, is an armored temnospondyl from what is now Guizhou province in China, then a salty Triassic sea. Two well-preserved skeletons carry strontium isotope ratios that match contemporary seawater, which the authors read as evidence the animals lived there year-round. Their 74-centimeter bodies were nearly covered in armor, a likely adaptation to salt stress.

The find extends a pattern already visible after the end-Permian mass extinction, when amphibians and reptiles flooded the oceans within a few million years. It also raises an open question: if a fully marine amphibian once existed, why does none exist today?

Why it matters

If a fully marine amphibian lived in the Triassic, amphibian salt tolerance was far wider than any living species suggests—forcing a rethink of how land vertebrates regained the seas.

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Key Indicators

74 cm

Body length of Gerrothorax maritimus

The armored temnospondyl measured about three-quarters of a meter, flattened and covered in bony plates.

8,000+

Living amphibian species, none fully marine

Every modern amphibian needs freshwater breaks; none is exclusively marine.

237

Age of the fossils, in millions of years

The specimens date to the Late Triassic, when the Guizhou site was a salty sea.

Voices

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People Involved

Ryosuke Motani

Palaeobiologist, University of California, Davis; co-author of the study

Co-author of the Gerrothorax maritimus paper

Steve Brusatte

Palaeontologist and evolutionary biologist, University of Edinburgh

Independent commentator on the discovery

Organizations Involved

University of California, Davis

Public research university

Home institution of study co-author Ryosuke Motani

A California public research university whose paleobiology group studies the physiology of extinct marine vertebrates.

University of Edinburgh

Public research university

Source of independent commentary on the discovery

A Scottish research university whose paleontology group studies Triassic ecosystems and the rise of dinosaurs.

Nature Ecology & Evolution

Peer-reviewed scientific journal

Publisher of the Gerrothorax maritimus study

A Nature Research journal covering ecology and evolutionary biology, including paleontology.

Timeline

1 event Latest: Today

October 2026
Nature reports armored amphibian lived in Triassic seas
Today Publication

Researchers publish strontium isotope evidence that Gerrothorax maritimus, an armored temnospondyl from Guizhou, China, grew up drinking seawater about 237 million years ago.
Today

Scenarios

Gerrothorax maritimus formally joins the fossil record

Likely Resolves by End of 2028

Discussed by: Paleontologists quoted by Nature, including Steve Brusatte

The species name is provisional. A formal taxonomic description—naming the species in a peer-reviewed paleontology journal—would cement it. Given the quality of the two skeletons, this is the most likely near-term outcome.

Rival researchers challenge the marine reading

Possible Resolves by Q2 2029

Discussed by: Nature's reporting; Brusatte's conditional endorsement

Critics may argue the strontium ratios reflect chemical alteration after burial, or that the site was brackish rather than fully marine. Such a challenge would hinge on alternative taphonomic or isotopic interpretations of the two specimens.

More fully marine amphibians turn up elsewhere

Possible Resolves by Jan 1, 2030

Discussed by: The study's authors, who note salt tolerance existed among early Triassic temnospondyls

Prompted by the Guizhou find, teams may re-examine Late Triassic marine sites in Europe, North America and elsewhere for other armored temnospondyls, extending the pattern beyond a single locality.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

~249 million years ago

Svalbard oceanic tetrapod ecosystem (~249 Ma)

A condensed bone bed on Spitsbergen preserved a wide marine community—apex-predator ichthyosaurs, euryhaline temnospondyls, coelacanths, lungfish and sharks—just a few million years after the end-Permian extinction.

Then

Showed marine vertebrates recovered and diversified far faster than a slow, stepwise model of recovery allowed.

Now

Established that temnospondyl amphibians could tolerate salt water and live in oceanic settings early in the Triassic.

Why this matters now

Confirms amphibians entered marine environments early in the Triassic; the Guizhou find extends the pattern to a fully marine, armored species much later in the period.

November 2014

Cartorhynchus lenticarpus (2014)

Researchers in Anhui Province, China, reported a 0.5-meter amphibious ichthyosaur with seal-like flippers and heavy ribs, built both to crawl on land and swim in rough sea water, living about 248 million years ago.

Then

Filled an evolutionary gap between land reptiles and fully aquatic ichthyosaurs.

Now

Showed vertebrates re-entered the sea within roughly 4 million years of the end-Permian extinction.

Why this matters now

Like the Guizhou amphibian, it came from South China and reframed how and when land vertebrates recolonized the oceans after the worst mass extinction in Earth's history.