New Fossils From Bighorn Basin Sheds Light On Evolution Of Early Carnivorous Mammals

Between 50 and 55 million years ago, during the early Eocene, ancient mammalian carnivores known as hyaenodontids reigned through North America. These animals were the early predecessors of modern day mammalian carnivores such as lions, tigers, bears, weasels, raccoons and wolves, but, until now, teeth fossils represented the only evidence of their existence.

However, a nearly complete skeleton belonging to the genus of hyaenodontids Galecyon – meaning "polecat dog" – was recently unearthed from the Bighorn Basin in Wyoming. Following a detailed analysis, researchers from the University of Arizona are revealing new data on the ecology and evolutionary relationships of these early carnivores, according to their news release. 

"The skeleton of Galecyon shows why we keep looking for fossils even in places where we already have a lot of specimens. When this skeleton was found, tens of thousands of mammalian fossils had been collected from the Bighorn Basin, but this was the first decent skeleton of this animal," Shawn Zack, lead author of the recent study, explained.  

Compared to fossil teeth, the skeleton provides a better understanding of the coyote-sized animal's full anatomy and the kinds of movements and behavior its build would have allowed.

"Galecyon may have moved around like a living wolverine or skunk," Zack added in a statement, "probably not much of a runner, but spending most of its time on the ground, while some of its relatives spent a lot more time in the trees."

For their study, Zack was accompanied by co-author Ken Rose of Johns Hopkins University. In addition to learning more about how the animals lived, the scientists were able to interpret how hyaenodontid members differed from each other. 

"This study shows that postcranial and dental morphology support different patterns of hyaenodontid relationships. That is an indication that there is still a lot to learn about hyaenodontid evolution," Zack concluded, adding that, "This study shows that early hyaenodontids had diverse habitat preferences, which helps explain how several different hyaenodontids were able to coexist in the same faunas, despite having similar diets and comparable body sizes."

Their findings were recently published in the Journal of Vertebrate Paleontology. 

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