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Early relatives of primates lived in the Arctic 52 million years ago


Analysis of fossilised teeth from Ellesmere Island, Canada, reveals that extinct relatives of monkeys and apes reached the Arctic during a period when the climate was hotter



Life



25 January 2023

Artist’s reconstruction of Ignacius dawsonae

Kristen Miller, Biodiversity Institute, University of Kansas

Tree-dwelling relatives of primates lived in swampy forests in the Arctic 52 million years ago when the climate was about 13°C warmer than today.

“These creatures are the first and only primate relatives known to make it to the Arctic,” says Kristen Miller at the University of Kansas.

Primates, which include monkeys and apes, are descended from squirrel-like mammals that survived the mass extinction that killed most dinosaurs 66 million years ago.

Miller and her colleagues took pictures of around 40 teeth and jaw fossils that had been previously collected from Ellesmere Island, Canada, which sits within the Arctic circle. Previous studies had dated the fossils to 52 million years ago, but didn’t identify what species they were from.

By using a statistical analysis to compare the size and curvature of the fossilised teeth with those of extinct and living primate relatives, the team discovered two new species of primate relatives, which they named Ignacius mckennai and Ignacius dawsonae after the palaeontologists who first collected them.

“Mammals have a very complicated tooth anatomy, which means we can use teeth like fingerprints at a crime scene to tell one species from another,” says Chris Beard, also at the University of Kansas.

Other species in the genus Ignacius have been found elsewhere in North America, but their exact relationship with modern primates is subject to debate.

The team’s analysis suggests the Arctic-dwelling species probably evolved from a chipmunk-like ancestor that migrated northwards from mid-latitude regions of North America as the climate warmed. Compared with their common ancestor, I. dawsonae would have been twice as large and I. mckennai four times as big, says Beard.

The tooth analysis also revealed that the creatures probably evolved to eat a diet of hard nuts and tree bark to cope with a lack of softer fruits – presumed to be their preferred food – during the six months when sunlight is lacking so far north.

The findings provide insights into how animals may cope with global warming. “A few kinds of animals are likely to move northwards into the Arctic, but many others will not be able to – in the same way our Ignacius species made it but many other primates living at lower latitudes didn’t,” says Beard. Other animals living on Ellesmere Island at the time included crocodiles and tapirs, says Miller.

“This is significant for broadening our perspective on primate biology and geographic ranges in the past,” says Kenneth Rose at Johns Hopkins University in Maryland. “The diagnoses of the two new species are appropriate and scientifically sound. The dietary inferences are reasonable.”

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