MADRID, 25 (SERVIMEDIA)
An international team of researchers has found fossils of two sister species, early relatives of primates that lived north of the Arctic Circle around 52 million years ago, dubbed ‘primatomorphs’.
That’s how they explain it in a peer-reviewed article published this Wednesday in the journal PLOS ONE.
The authors point out that the first primates adapted to life in the high Arctic of present-day Canada, which had a warm climate but limited biodiversity.
The early Eocene was a period of intense global warming and provided a crucial case study for studying how ecosystems respond to climate change.
Kristen Miller of the University of Kansas in the United States and her colleagues identify two new species, the first primate relatives ever known from this ancient Arctic ecosystem.
According to Miller, both species (‘Ignacius mckennai’ and ‘Ignacius dawsonae’) descend from a common northbound ancestor who possessed the spirit to “go boldly where no primate has gone before”.
Early Eocene
The samples were discovered on Ellesmere Island, Canada, in sediment layers associated with the early Eocene, a period of warmer temperatures that could predict how ecosystems will fare in the coming years due to human-induced climate change.
“Relatives of primates have never been found at such extreme latitudes,” notes Miller, before adding, “In tropical regions, they’re more likely to be found 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, in places like New Mexico, Colorado, Wyoming, and Montana. Even in Texas we have some fossils that also belong to this family.”
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. .
This ambiguity, Miller suggests, may have led to both species developing 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 keep the best ones,” says Miller, who analyzed high-resolution microtomography of the fossil teeth described in the paper.
“His teeth are super weird compared to his closest relatives. So what I’ve been doing for the last two years is understanding what they were eating and if they were eating different materials than their mid-latitude counterparts.”
Miller and his colleagues believe that food was much harder to find during the dark winter months, when Arctic primate relatives were likely forced to consume harder material.
“We think this is probably the greatest physical challenge of the ancient environment for these animals,” says Chris Beard, Distinguished Professor of Ecology and Evolutionary Biology at the University of Kansas, who notes, “How do you survive even six months of winter darkness? when it’s hot enough? The teeth and even the jaw muscles of these animals have changed compared to their close relatives in the mid-latitudes.”
Beard notes, “To survive those long arctic winters when preferred foods like fruit were unavailable, they had to rely on ‘alternative foods’ like nuts and seeds.”
Additionally, the researchers noted that both species were slightly larger than their closest relatives further south, a group of cousins of primates called Plesiadapiforms.
“But they were pretty small. Some ‘plesiadapiforms’ in mid-latitude North America are very small. Of course, none of these species are related to squirrels, but I think it’s the creature closest to us that helps us imagine what they might have been like. Most likely they were very arboreal and therefore lived in trees most of the time.”