New research indicates that the now-extinct giant sea scorpion had the ability to traverse oceans, providing new insights into the global distribution of a species that once dominated the ancient seas.
Most modern scorpions are small enough to fit in the palm of a human hand.
Illustration of Jaekelopterus rhenaniae – a species of sea scorpion that lived about 390 million years ago and is one of the largest arthropods ever discovered. (Photo: Ja Chirinos/Science Source).
However, beneath the oceans in the Paleozoic Era over 400 million years ago, giant sea scorpions – apex predators – could grow larger than adult humans, according to the New York Times.
“Essentially, they operated like sharks“, said Russell Bicknell, a paleontologist at the American Museum of Natural History.
Based on fossil records from Australia, Dr. Bicknell and his colleagues published new research in the journal Gondwana Research showing that the largest sea scorpions were capable of crossing oceans.
He described this finding as “completely surpassing the limits of what we know about what arthropods can do.”
From Ocean Dominators to Extinction
Sea scorpions are actually a diverse group of arthropods known scientifically as eurypterids. They come in various shapes and sizes but are best known for their large individuals, which could grow over 2.7 meters long. With their massive claws, sturdy exoskeletons, and strong swimming legs, these giant sea scorpions likely dominated the ancient oceans.
Although this arthropod species may have been a terrifying predator during the Paleozoic, they went extinct without leaving many traces.
The fossil record of eurypterids shows that they peaked during the Silurian Period, beginning around 444 million years ago, and then suddenly went extinct after the end of the Devonian Period, approximately 393 million years ago.
This abrupt change in fate has puzzled scientists.
Size comparison of the largest extinct sea scorpion with a human. (Photo: Slate Weasel).
“They appeared, began to thrive, became very large, and then they went extinct,” said James Lamsdell, a paleobiologist at West Virginia University who did not participate in the study. “For a time, they dominated, and then they simply vanished.”
Since then, giant arthropods have not been seen again, and understanding more about where the giant sea scorpions appeared could lay the groundwork for explaining why this occurred.
Ability to Cross Oceans
Most eurypterid fossils have been found in North America and Europe, with a few recently excavated in China.
Some eurypterid fossils were previously reported in Australia, but they were just too small and vague to determine whether they belonged to the largest sea scorpion species.
Dr. Bicknell’s study recorded a new set of eurypterid fossils from Australia. Although they are also just fragments, he suspects they can be identified more clearly.
Upon careful examination, the fragments are primarily the exoskeletal parts, including a piece that could be a head with signs of an eye. Dr. Bicknell believes these fragments belong to two eurypterid species: Pterygotus and Jaekelopterus – the largest known sea scorpion.
Dr. Bicknell’s analysis of the rock structure where the fossils were found indicates that they are fundamentally similar to locations previously discovered: shallow marine areas and floodplains along continental coastlines.
One set of fossils was found alongside armored fish, while another set contained some fossilized feces with debris from a trilobite (Class Trilobita), suggesting these sea scorpions may have preyed on hard-shelled creatures.
A fossil sample possibly belonging to the Jaekelopterus found in Australia, showing signs of an eye. (Photo: R.D.C. Bicknell et al./Gondwana Research, 2024).
Dr. Lamsdell noted that these fragments are better than what was previously found, although discovering more specimens in Australia would help strengthen the conclusions.
If Dr. Bicknell is correct, these fossils would extend the range of giant sea scorpions all the way to the ancient supercontinent Gondwana – where they had previously never been found.
This discovery also supports the idea that sea scorpions had the ability to cross oceans – a “feat” not to be underestimated. At that time, the journey between Gondwana and the supercontinent Euramerica could span thousands of miles, depending on the route.
“It’s exciting to see that they really traveled very far,” said Dr. Bicknell. “They made it to Gondwana.”
Dr. Bicknell hopes that further research will reveal whether the giant sea scorpions arrived here in a single migration or moved seasonally.
The fact that these giant sea scorpions undertook this journey also suggests that their great size could have played a crucial role in the process of migration.
According to Dr. Lamsdell, it could simply be that these animals required a large body to survive in the ocean, similar to modern-day sharks and whales. Once they grew large enough, they were capable of making this long journey.
But the specific reasons why such large sea scorpions could spread across the globe and then went extinct shortly afterward, in geological time scales, remains a mystery that scientists strive to unravel.
Gaining a better understanding of their range will only provide scientists with new locations to search for fossils, thus helping to shed light on many unanswered questions.
“Over time, there will be more discoveries,” Dr. Lamsdell said. “Then we will have a clearer idea of what happened to this animal.”
