February 4, 2023

Newswise – LAWRENCE – Two sister species of near-primates called “primatomorphans,” dating back about 52 million years, have been identified by University of Kansas researchers as the oldest to have lived north of the Arctic Circle. The results appear today in the peer-reviewed journal PLUS ONE.

According to lead author Kristen Miller, a PhD student at KU’s Biodiversity Institute and Natural History Museum, both species — Ignacius mckennai and I. dawsonae — descend from a common northbound ancestor that possessed the spirit to “boldly go where else no primacy was before”.

The samples were discovered on Ellesmere Island, Nunavut, Canada, in sediment layers associated with the early Eocene, an epoch of warmer temperatures that could predict how ecosystems will fare in the coming years due to human-induced climate change.

“No primate relative has ever been found at such extreme latitudes,” Miller said. “In tropical regions, you tend to find them around the equator. I was able to perform a phylogenetic analysis that helped me understand how the Ellesmere Island fossils are related to species found in mid-latitudes of North America—places like New Mexico, Colorado, Wyoming, and Montana. Even down in Texas we have some fossils that belong to this family as well.”

The Arctic Circle was much warmer when these close evolutionary cousins ​​of primates lived — a boreal ecosystem that harbored an abundance of early Cenozoic vertebrates, including ancient crocodiles — but, like today, it was still mostly dark for half the year. According to Miller, this obscurity may have caused both species to develop more robust teeth and jaws compared to other primate relatives of the time.

“A lot of what we do in paleontology is look at the teeth — they get the best,” said Miller, who analyzed the high-resolution microtomography of the fossil teeth described in the paper. “Their teeth are just super weird compared to their closest relatives. So what I’ve been doing over the past few years is understanding what they were eating and whether they were eating different foods than their mid-latitude counterparts.”

Miller and her co-authors believe that finding food was much harder during the bleak winter months, when Arctic primate relatives were likely forced to consume harder material.

“This is, in our opinion, probably the greatest physical challenge of the ancient environment for these animals,” said corresponding author Chris Beard, Senior Curator of Vertebrate Paleontology at the Biodiversity Institute and Foundation Distinguished Professor of Ecology & Evolutionary Biology at KU. “How do you get through six months of winter darkness even if it’s reasonably warm? The teeth and even the jaw muscles of these animals changed compared to their close mid-latitude relatives. To survive those long arctic winters when preferred foods like fruit were unavailable, they had to rely on “substitute foods” like nuts and seeds.”

Miller and Beard’s other co-author is Kristen Tietjen, a science illustrator at the Biodiversity Institute.

The researchers also found that both species were slightly larger than their closest relatives further south – a group of cousins ​​of primates dubbed “plesiadapiforms.”

“But they’re still pretty small,” Miller said. “Some plesiadapiforms from mid-latitude North America are really, really tiny. Of course, none of these species are related to squirrels, but I think this is the closest animal we have that will help us imagine what they might have been like. They were most likely very arboreal – living in the trees most of the time.”

The researchers believe the adaptations of both Arctic species during a period of global warming show how some animals could likely evolve new traits in response to climate change caused by human activity.

“It shows how something like a primate or a relative of primates that is specialized in one environment can change because of climate change,” Miller said. “I think it probably means that the range of primates could expand with climate change, or at least move towards the poles instead of the equator. Life is starting to get too hot there, perhaps we will have many taxa moving north and south instead of the intense biodiversity we are seeing at the equator today.”

Because both fossil species are new to science, researchers gave them scientific names honoring a pair of paleontologists who worked on Ellesmere Island decades ago. One of these eponymous paleontologists was a KU alumna and a pioneer for women in the field of paleontology.

“Mary Dawson was an amazing person,” Beard said. “She received her doctorate from the KU back in the 1950s and was one of the first, if not the first, American woman to receive a doctorate. in paleontology – and one of the first women to make a name for herself as a paleontologist in the United States. In my earlier career at the Carnegie Museum, where she spent her entire career, I worked closely with Mary for more than 20 years. Mary was the director of a large project on Ellesmere Island. Of course we wanted to name one of the species after her. The other species is named after Malcolm McKenna, a contemporary, close friend and colleague of Mary Dawson, and a former mentor of mine.”

In fact, the fossil species Ignacius mckennai and I. dawsonae were part of a collection of fossils left by Dawson and McKenna for further analysis.

“Mary and Malcolm left me these fossils and asked me to study them,” Beard said. “I said, ‘Yes, of course – I like doing that.’ They just sat there like fine wine and got better and better over time until Kristen showed up – and it was clear Kristen had everything it took to get the ball across the finish line.”

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