Almost 40 years ago, researchers discovered a perfectly preserved collection of fossils inside an impact crater in the Canadian High Arctic. Now, the remains have finally revealed their secret and are revealed to belong to an extinct hornless rhinoceros that lived 23 million years ago.
Scientists named the animal Epiatheracerium itjilik, a species name that means “frost” or “frosty” in Inuktitut. The creatures were about the same size as the modern Indian rhino (Rhinoceros unicornis), the Canadian Museum of Nature (CMN) said in a statement. The newly identified fossil, the only specimen ever discovered, indicates that the animal died of unknown causes as a young adult.
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The bones were preserved in a 14-mile (23-kilometer) wide impact crater that rapidly filled with water. The crater was formed by an asteroid or comet around the same time the arctic rhino lived, suggesting that the rhino died inside the crater before it became a lake.
The statement said the region’s climate at the time was much warmer than it is today, and plant remains indicate there was a temperate forest in Canada’s high Arctic, specifically on Nunavut’s Devon Island, where the crater is located.
As the Miocene Epoch (23 million to 5.3 million years ago) gave way to the Pliocene Epoch (5.3 million to 2.6 million years ago) and finally the last ice age, the fossils were broken up by freeze-thaw cycles and gradually pushed up to the surface of the crater. Researchers discovered the fossil in 1986.
Subsequent field visits to the crater uncovered more bones belonging to Arctic rhinoceros specimens. These expeditions also unearthed another species that lived 23 million years ago, the walking seal (Puijila darwini), which is thought to have lived alongside the arctic rhinoceros.
Gilbert and colleagues described E. itjilik based on characteristics of its teeth, mandible, and skull compared to other rhinoceros species. The researchers then determined the arctic rhino’s place in the rhino evolutionary tree by analyzing the relationship between the newly discovered species and 57 extinct and extant rhino groups. They published their results on Tuesday (October 28) in the journal Nature Ecology and Evolution.
This discovery suggests that E. itjilik is most closely related to rhinos that lived in modern-day Europe before 23 million years ago. True modern rhinos (family Rhinocerosidae) evolved in North America and Southeast Asia about 40 million years ago, and their descendants have since spread to every continent except South America and Antarctica.
“Currently, there are only five species of rhinos in Africa and Asia, but they were once found in Europe and North America, and more than 50 species are known from the fossil record,” study lead author Daniel Fraser, research scientist and head of paleontology at CMN, said in a statement.
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The newly discovered arctic rhinoceros is the most northerly rhinoceros ever discovered. Researchers believe the species migrated from Europe via the North Atlantic Land Bridge, an ancient passageway across Greenland made of exposed continental crust.
The North Atlantic Land Bridge appeared during the Late Cretaceous period (145 million to 66 million years ago), but there is debate as to when it disappeared. Some studies indicate that the land bridge collapsed 56 million years ago. Others suggest that the bridge was more or less continuous until about 2.7 million years ago.
That’s because the rhinoceros family arrived in Europe 33.9 million years ago during an extinction and dispersal event known as the Grand Coupeur, or “Great Cut.” The new study suggests that these rhinos had reached North America by 23 million years ago, so the land bridge likely persisted until at least the beginning of the Miocene.
“Descriptions of new species are always exciting and informative,” Fraser said. “Our reconstruction of rhino evolution shows that the North Atlantic played a much more important role in rhino evolution than previously thought.”
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