Oldest arctic primate relatives: Ancient primatomorphans brave the cold and darkness

Researchers at the University of Kansas have identified two sister species of near-primate called “primatomorphans” as the oldest to have lived north of the Arctic Circle. The findings, published in the journal PLOS ONE, reveal that the species, named Ignacius mckennai and I. dawsonae, descended from a common ancestor with a pioneering spirit.

The fossils of these species were discovered on Ellesmere Island in Canada, dating back to the early Eocene epoch. This period experienced warmer temperatures, which makes the findings significant in understanding how ecosystems might respond to human-induced climate change in the future.

Lead author Kristen Miller, a doctoral student at KU’s Biodiversity Institute and Natural History Museum, noted that primate relatives are typically found in tropical regions around the equator. This discovery of primatomorphans at extreme latitudes provides valuable insights into their distribution and evolution.

The Arctic Circle during the primatomorphans’ time was considerably warmer, yet characterized by long periods of darkness. The researchers suggest that the darkness may have influenced the evolution of their teeth and jaws, resulting in more robust dental structures compared to their primate relatives.

Miller used high-resolution microtomography to analyze the fossil teeth, revealing their unique characteristics. The teeth of these primatomorphans differed significantly from those of their close relatives, indicating potential differences in diet and food availability.

The researchers hypothesize that the scarcity of food during the dark winter months in the Arctic led these primatomorphans to consume harder materials. They propose that the ability to survive the challenging Arctic winters relied on adaptations to rely on alternative food sources such as nuts and seeds when preferred foods like fruits were unavailable.

Overall, this study sheds light on the ancient Arctic ecosystem and the adaptive strategies of primatomorphans in a challenging environment.

Another co-author of the study is Kristen Tietjen, a scientific illustrator at the Biodiversity Institute, who contributed to the visual representation of the research.

The researchers also discovered that both species of primatomorphans were slightly larger than their closest relatives found farther south, a group of primate cousins known as “plesiadapiforms.” However, Miller notes that even though they were larger, these primatomorphans were still relatively small. She compares their size to squirrels and envisions them as arboreal creatures, spending most of their time in trees.

The adaptations observed in these Arctic species during a period of global warming provide insights into how animals can evolve in response to climate change, particularly the climate change driven by human activities today. Miller suggests that this research highlights the potential for primates or primate relatives to expand their range or move towards the poles as the equatorial regions become too hot. This could result in significant shifts in biodiversity patterns.

As these two fossil species were previously unknown to science, the researchers decided to name them after two paleontologists who conducted extensive work on Ellesmere Island in the past. One of the paleontologists, Mary Dawson, was a KU alumna who made significant contributions to the field of paleontology and paved the way for women in the discipline. The other species was named after Malcolm McKenna, a close friend and colleague of Mary Dawson and an influential mentor to Chris Beard.

The fossils of Ignacius mckennai and I. dawsonae were part of a collection left behind by Dawson and McKenna for further study. Beard, who had a long-standing relationship with Mary Dawson, took on the responsibility of studying these fossils, and ultimately, Miller’s expertise allowed for the completion of this research project.

Source: University of Kansas

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