About 23 million years ago, a rhinoceros stomped across the Canadian High Arctic. Now extinct, a team of scientists from the Canadian Museum of Nature (CMN) have found a new species of the enigmatic āArctic rhino.ā First uncovered almost 40 years ago in lake deposits in Haughton Crater on Devon Island, Nunavut, Epiatheracerium itjilik was more petite than many of its modern descendants. The species is described in a study published today in the journal Nature Ecology & Evolution.
āToday there are only five species of rhinos in Africa and Asia, but in the past they were found in Europe and North America, with more than 50 species known from the fossil record,ā Dr. Danielle Fraser, a study co-author and head of palaeobiology at the Canadian Museum of Nature, said in a statement. āThe addition of this Arctic species to the rhino family tree now offers new insights to our understanding of their evolutionary history.ā
Big rhinos, small rhinos, and everything in between
Rhinoceroses have been around for over 40 million years and have been found on all continents except South America and Antarctica. This recently discovered Arctic rhino lived about 23 million years ago, during the Early Miocene. It is most closely related to other rhino species that thrived in Europe millions of years earlier.
Earthās Rhinocerotids also came in a variety of shapes and sizes. Some were large and hippo-like, while others were relatively small and lacked horns. Epiatheracerium itjilik falls in that latter category. It was relatively small and slight, similar to the modern Indian rhinoceros, but without a horn. The team believes that the Arctic specimen was in early to mid-adulthood when it died based on moderate wear of the cheek teeth.
Most of the bones were collected at the Haughton Impact Crater site in 1986 by the late arctic paleontologist Dr. Mary Dawson. The Haughton Crater was formed by an asteroid or comet strike about 31 to 32 million years ago during the Early Oligocene. It is almost 14 miles across and the most northern known site containing fossils from the Miocene Epoch (about 23 to 5.6 million years ago). At this time, many families of modern mammals began to diversify and move between Earthās continents. When the impact crater filled with water a few million years after impact, a lake that preserved the remains of local plants and animals formed.
Dawson had uncovered the critical diagnostic parts of the skeletonāthe upper and lower teeth, mandibles, and parts of the skull almost 40 years ago. With these, the team from CMN could define it as a rhinocerotid and a completely new species.
āWhatās remarkable about the Arctic rhino is that the fossil bones are in excellent condition,ā palaeobiologist Marisa Gilbert added. āThey are three dimensionally preserved and have only been partially replaced by minerals. About 75% of the skeleton was discovered, which is incredibly complete for a fossil.ā
During the late 2000s, Gilbert took part in a number of research trips to the Haughton Crater with study co-author Dr. Natalia Rybcynski. These expeditions uncovered another new species, a walking seal ancestor named Puijila darwini. Additional remains of E. itjilik were found on later field expeditions.
Crossing a land bridge
With this new Arctic species, the team dug deeper into the evolutionary and biogeographic history of rhinocerotids. Biogeography studies how animals and plants evolved and dispersed over time.
To place E. itjilik on the rhino family tree, they studied the occurrence of 57 other types of rhinocerotids, almost all of which are extinct. They combed through museum collections, scientific literature, and various databases.
The teamās detective work and analysis shows how rhinos dispersed over millions of years. They likely travelled between present day North America and Europe (through Greenland) on the North Atlantic Land Bridge. Earlier studies suggested that this land bridge may have only been used as a pathway until about 56 million years ago. However, E. itjilik and its related species suggest that rhinos moved from Europe to North America much more recently, potentially as late as the Miocene.
āItās always exciting and informative to describe a new species. But there is more that comes from the identification of Epiaceratherium itjilik, as our reconstructions of rhino evolution show that the North Atlantic played a much more important role in their evolution than previously thought,ā said Fraser. āMore broadly, this study reinforces that the Arctic continues to offer up new knowledge and discoveries that expand on our understanding of mammal diversification over time.ā
Honoring the High Arctic
The species name itjilik means āfrostyā or āfrostā in Inuktitut. To honor the rhinoās home in the High Arctic, the team consulted with Inuit Elder Jarloo Kiguktak. Kiguktak is also the former mayor of Grise Fiord, the most northerly Inuit community in Canada. He has also visited the fossil deposits of Haughton Crater and played a role in multiple paleontological expeditions in the High Arctic.
The fossil of Epiceratherium itjilik is currently housed and curated in the fossil collections of the Canadian Museum of Nature.Ā
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