Several 250-million-year-old specimens from museum collections in Australia and the United States reveal the remarkable diversity of the Western Australian trematosaurid temnospondyl, indicating that early marine amphibians spread across the continent shortly after the end-Permian mass extinction.
ancient marine amphibians Eryslovatracos (foreground) and Aphaneramma (Background) 250 million years ago, they swam along the far northern coast of what is now Western Australia. Image credit: Pollyanna von Knorring, Swedish Museum of Natural History.
“The catastrophic end-Permian mass extinction and extreme global warming prompted the emergence of modern marine ecosystems at the beginning of the Mesozoic Era, about 252 million years ago,” Dr. Benjamin Kjaer of the Swedish Museum of Natural History and colleagues said in a statement.
“This landmark evolutionary event included the early appearance of sea-going tetrapods (limbed vertebrates), including both amphibians and reptiles, which quickly became dominant as aquatic apex predators.”
“To date, these earliest sea monster fossils have been recorded primarily in the Northern Hemisphere.”
“In comparison, the Southern Hemisphere record is geographically sparse and incompletely known.”
In a new study, paleontologists analyzed marine amphibian fossils from the iconic Kimberley region of Western Australia’s far north.
“These fossils were first discovered in Australia during scientific expeditions conducted in the early 1960s and 1970s,” the researchers said.
“The recovered specimens were distributed to museum collections in Australia and the United States.”
“The resulting research was finally published in 1972 and identified a single species of marine amphibian. Eryslovatrachus nooncambahensisIt was named after several skull fragments that were found weathered from a rocky outcrop at Noonkumba Farm, east of the isolated Kimberley township of Derby. ”
“Unfortunately, the original fossil was Eryslovatracos It was lost at some point during the intervening 50 years. ”
“This began a survey of international museum collections, culminating in the rediscovery and reassessment of these mysterious ancient marine amphibian remains in 2024.”
According to scientists, Eryslovatracos It was a temnospondylus of the trematosaurid family.
“Trematosaurids were superficially ‘crocodile-like’ relatives of modern salamanders and frogs that grew up to 2 meters (6.6 feet) long,” the researchers said.
“These fossils are important because they occur in rocks that were deposited as coastal sediments less than a million years after the end-Permian mass extinction.”
“They are therefore geologically the oldest of the currently recognized groups of Mesozoic marine tetrapods.”
But surprisingly, detailed studies showed that skull fragments were found. Eryslovatracos Not all belonged to a single species.
Rather, they represented at least two different types of trematosaurids. Eryslovatracos and another species belonging to a well-known genus Aphaneramma.
“Inspection of” Eryslovatracos “Using high-resolution 3D imaging, the skull was approximately 40 centimeters (16 inches) long when completed, suggesting it belonged to a large-bodied, broad-headed top predator,” the authors said.
“on the other hand, Aphaneramma They were about the same size, but had elongated snouts for catching small fish. ”
“Both of these trematosaurs swam in the water column, but would have hunted different prey in the same habitat.”
“Furthermore, on the other hand, Eryslovatracos Fossils known only from Australia Aphaneramma It has been reported from similar old deposits in the Scandinavian Arctic, Svalbard, the Far East, Pakistan, and Madagascar. ”
“Australian trematosaurid fossils show that these earliest Mesozoic marine tetrapods not only rapidly radiated into a range of ecological niches, but also dispersed around the world along the coastal margins of interconnected supercontinents, probably during the first two million years of the dinosaur era.”
team’s paper this month, Journal of Vertebrate Paleontology.
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Benjamin P. Care others. Revision of Trematosauridae Eryslovatrachus nooncambahensis A mysterious marine hand vertebra community inhabiting the Lower Triassic of Western Australia has been confirmed. Journal of Vertebrate Paleontologypublished online on February 22, 2026. doi: 10.1080/02724634.2025.2601224