Fossil of Sea Monster Reveals Australia's Desert Was Once a Tropical Sea

Approximately 250 million years ago, the Kimberley region of Western Australia, now known for its arid, dusty, and remote landscape, looked vastly different. Where there are now barren plains and cattle ranches, a shallow bay with warm tropical waters once stretched. In these waters, crocodile-like creatures swam as apex predators.

The rediscovery of fossils of ancient marine amphibians from the Early Triassic period reveals a dramatic story of how life rebounded after the largest mass extinction event in Earth’s history—the end-Permian extinction.

Around 252 million years ago, Earth experienced an event known as the end-Permian mass extinction. This event was triggered by extreme global warming and massive environmental changes that devastated both marine and terrestrial ecosystems.

According to Dr. Benjamin Kear from the Swedish Museum of Natural History and his team, “The devastating end-Permian mass extinction and extreme global warming triggered the emergence of modern marine ecosystems in the early age of dinosaurs (the Mesozoic Era).”

He added, “This significant evolutionary event involved the first appearance of marine tetrapods—vertebrates with limbs—including amphibians and reptiles, which quickly became aquatic apex predators.”

For decades, most of these early “sea monster” fossils have been found in the Northern Hemisphere. Records from the Southern Hemisphere, including Australia, have been limited and poorly understood.

Recent research is now beginning to change that picture.

In 1972, scientists published a study identifying a new species based on a fragment of a skull: Erythrobatrachus noonkanbahensis.

However, mysteriously, the original Erythrobatrachus fossil was lost over the next 50 years.

Instead of ending the story, the loss triggered a major search of international museum collections. In 2024, researchers finally managed to locate and re-examine the fossils using high-resolution 3D imaging technology.

The results were surprising.

The scientists explained, “Trematosaurids are modern relatives of salamanders and frogs that resembled crocodiles and could grow up to 2 meters long.”

This group is significant because its fossils were found in coastal rock layers formed less than one million years after the end-Permian mass extinction. This means they are the oldest geologically identifiable group of Mesozoic marine tetrapods.