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Giant ‘terrifying’ 8-foot sea scorpions ‘substantially larger than humans’ found – but doomed creature sparks mystery

Fossils of the mighty sea creatures, formally known as eurypterids, were rarely found in Australia until now

THE discovery of the remnants of enormous ancient scorpions has left scientists with more questions than answers.

An international team of paleontologists uncovered evidence of eight-foot-long arthropods that lived roughly 400 million years ago.

Scientists have uncovered the remains of two eurypterids, or sea scorpions, that lived around 400 million years ago in Australia
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Scientists have uncovered the remains of two eurypterids, or sea scorpions, that lived around 400 million years ago in AustraliaCredit: Getty

The gargantuan creatures are called eurypterids, colloquially known as sea scorpions.

They belong to an extinct group of aquatic arthropods, making them ancient relatives of crabs, lobsters, and spiders.

The latest fossils were imprinted in a rock layer in present-day New South Wales, Australia.

They date back to the Silurian era (443.8 to 419.2 million years ago) and Devonian era (419.2 to 358.9 million years ago) respectively.

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While some eurypterid fossils were previously found in Australia, they were too fragmented to classify, making the discovery all the more exciting.

The researchers note that the fossils were mostly of exoskeletons. One belonged to the genus Pterygotus, the other to Jaekelopterus.

Pterygotus could reach 1.7 metres in length, or around five feet, seven inches.

Jaekelopterus, on the other hand, could grow as long as 2.5 meters, or over eight feet - substantially larger than a person.

The researchers published their findings Saturday in the journal , revealing that their discovery came with several unanswered questions.

For starters, the fossils were nearly identical to others scattered around ancient Gondwana.

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The supercontinent splintered into present-day Africa, South America, Australia, Antarctica, the Indian subcontinent, and the Arabian Peninsula.

This suggests the sea scorpions were somehow able to swim thousands of kilometers.

The research team suggested that the scorpions' giganticism may have aided their migration.

However, the reverse scenario, in which long distances stoked the evolution of their formidable size, is also possible.

The gargantuan creatures could grow over eight feet long. Their fossils have mostly been found in North America and Europe, meaning their history in Australia is a mystery
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The gargantuan creatures could grow over eight feet long. Their fossils have mostly been found in North America and Europe, meaning their history in Australia is a mystery

It is currently unclear whether sea scorpions traversed the waters with the changing seasons or only crossed once.

Their sudden extinction remains one of the biggest mysteries.

Since their trail appears to end around 393 million years ago, scientists suspect they perished due to changes in their environment.

This is around the start of the Carboniferous period, characterized by low sea levels and the formation of glaciers.

Fossils are concentrated around ancient Gondwana, a supercontinent that splintered into two-thirds of the world's landmass - suggesting sea scorpions were able to cross long, watery distances
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Fossils are concentrated around ancient Gondwana, a supercontinent that splintered into two-thirds of the world's landmass - suggesting sea scorpions were able to cross long, watery distancesCredit: International Association for Gondwana Research

More than 200 species of sea scorpions have been recorded, but fossils rarely turn up in Oceania.

"Due to their size and preservational potential, eurypterids have been well-documented in European and North American deposits, with less evidence from Gondwana," the authors wrote.

"There is particularly limited evidence of the group from the Australian fossil record."

It is unclear why the mighty sea scorpions died out. Scientists believe their sudden extinction might be linked to environmental changes like shrinking sea levels
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It is unclear why the mighty sea scorpions died out. Scientists believe their sudden extinction might be linked to environmental changes like shrinking sea levelsCredit: Getty

While it is just a start, the discovery is a launching point for future research.

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Beyond painting a broader picture of eurypterids, the fossils help researchers understand the development of ancient life in Australia.

"We conclude that these new records evidence the diversity of larger arthropods in Australian deposits and that ongoing documentation of these rare fossils is required to further understand the Paleozoic of Australia," the authors wrote.

A timeline of Earth's development

Here's your cheat sheet to the major geologic periods on Earth

Pre-Cambrian Era (4.6 billion - 541 million years ago)

  • Hadean Eon (4.6 - 4 billion years ago): Formation of Earth.
  • Archean Eon (4 - 2.5 billion years ago): Formation of early continental crust; emergence of the first simple life forms (prokaryotes).
  • Proterozoic Eon (2.5 billion - 541 million years ago): Development of more complex life forms (eukaryotes); appearance of multicellular organisms.

Paleozoic Era (541 - 252 million years ago)

  • Cambrian Period (541 - 485 million years ago): Cambrian Explosion; rapid diversification of life, including the first hard-bodied organisms.
  • Ordovician Period (485 - 443 million years ago): Development of the first fish and the colonization of land by plants.
  • Silurian Period (443 - 419 million years ago): Evolution of the first vascular plants and the first land animals (arthropods).
  • Devonian Period (419 - 359 million years ago): Age of Fishes; first amphibians and significant plant diversification.
  • Carboniferous Period (359 - 299 million years ago): Formation of extensive coal swamps; diversification of amphibians and early reptiles.
  • Permian Period (299 - 252 million years ago): Rise of the first mammals and reptiles; ended with the largest mass extinction event.

Mesozoic Era (252 - 66 million years ago)

  • Triassic Period (252 - 201 million years ago): Early dinosaurs and mammals appear; recovery from the Permian extinction.
  • Jurassic Period (201 - 145 million years ago): Dominance of dinosaurs; first birds and flowering plants.
  • Cretaceous Period (145 - 66 million years ago): Continued evolution of dinosaurs and flowering plants; ends with the mass extinction event that wiped out the dinosaurs.

Cenozoic Era (66 million years ago - Present)

  • Paleogene Period (66 - 23 million years ago): Mammals and birds diversify; formation of modern continents.
  • Neogene Period (23 - 2.6 million years ago): Evolution of early hominids; development of modern flora and fauna.
  • Quaternary Period (2.6 million years ago - Present):
    • Pleistocene Epoch (2.6 million - 11,700 years ago): Ice Ages; development and spread of early humans (Homo erectus, Neanderthals, and Homo sapiens).
    • Holocene Epoch (11,700 years ago - Present): Rise of agriculture; development of civilizations and modern societies.
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