Above:听Artist's depiction of three new species of fossil condylarths: From left to right, Conacodon hettingeri, Miniconus jeanninae and Beornus honeyi. (Credit: Banana Art Studio)
Paleontologists at听抖阴旅行射 Boulder have at the site of an ancient riverbed in southern Wyoming.
The new species lived within a few hundred thousand years after a mass extinction event roiled the globe and killed off non-avian dinosaurs 66 million years ago. They were ancestors of today鈥檚 hoofed animals, such as cattle, horses, deer and moose鈥攂ut much smaller. They also offer a new window into what western North America looked like after dinosaurs vanished from the face of Earth, making way for the Age of Mammals.
鈥淧aleontologists spend a lot of time and effort studying dinosaurs and what caused their extinction,鈥� said Jaelyn Eberle, curator of fossil vertebrates at the 抖阴旅行射 Museum of Natural History and a professor of geological sciences. 鈥淚鈥檓 much more interested in what happened after.鈥�
Above: Jaelyn Eberle inspects a collection of mammal fossils at the 抖阴旅行射 Museum of Natural History. 叠别濒辞飞:听A fossil jawbone belonging to Beornus honeyi. (Photos by Glenn Asakawa/University of Colorado)
Eberle and former 抖阴旅行射 Boulder graduate student Madelaine Atteberry describe the new species in a study published today in the Journal of Systematic Palaeontology.
The three animals fall into a broad category of primitive ungulates informally called 鈥渃ondylarths.鈥� You probably wouldn鈥檛 recognize them next to modern-day grazers鈥攎ost of the early condylarths were mouse- to rat-sized had several toes rather than hooves.
But the team鈥檚 findings also suggest that paleontologists may have underestimated just how diverse the West was right after the extinction of the dinosaurs. Some habitats in Colorado and Wyoming may have been home to an eclectic group of mammals adopting a wide range of lifestyles.
And the researchers are just getting started.
鈥淭here are plenty more fossils from this locality waiting to be identified,鈥� said Atteberry, now the undergraduate program assistant in the Department of Geological Sciences at 抖阴旅行射 Boulder.
Post-Jurassic Park
The new research travels back to a period of time that paleontologists call the early Puercan North American Land Mammal Age鈥攚hich spanned the first 300,000 years or so after an asteroid crashed down to Earth, marking what scientists call the Cretaceous-Paleogene mass extinction event. A lot of questions remain about this pivotal period in the planet's history, Eberle said.
鈥淲e still don鈥檛 fully understand what happened after the extinction of the dinosaurs,鈥� Eberle said. 鈥淲e don鈥檛 have anything quite like condylarths living today, so there鈥檚 a lot of speculation about their biology and ecology.鈥�
To fill the gaps, Eberle and Atteberry dug into a collection of condylarth fossils, mostly pieces of jawbones and teeth, that paleontologists collected from Wyoming鈥檚 Great Divide Basin in the 2000s. Today, the site is a dry and scrubby patch of land not far from the town of Rawlins.
For Atteberry, one jawbone from the area immediately jumped out.
鈥淚t was larger than everything else in the box,鈥� she said. 鈥淚t had these large, really bulbous teeth, and we could see even with the naked eye that it was different than the rest.鈥�
Mammals arise
The teeth, Atteberry and Eberle discovered, belonged to a species of early condylarth that may have been about the size of a housecat. The duo named the owner of these inflated molars Beornus honeyi鈥攁 nod to Beorn from J.R.R. Tolkein鈥檚 The Hobbit, a character who is sometimes 鈥渁 great strong man鈥� and sometimes 鈥渁 huge black bear.鈥�
The researchers also identified two other new species from the region, which they dubbed Miniconus jeanninae and Conacodon hettingeri, alongside several more common species. All three belong to the family Periptychidae.
鈥淭his region was much more diverse in mammal species than what we usually see in the early Puercan,鈥� Eberle said.
Based on the shape of their teeth, the three new species may have been omnivores that ate both meat and plants鈥攁lthough some members of the periptychid family at the time may also have fed on tough, fibrous vegetation like many ungulates do today.
Eberle added that many paleontologists have assumed that, during the early Puercan, much of the West was home to the same handful of common mammal species, all the size of rodents. But the new fossil finds suggest that mammals may have begun to spread around the region, developing larger and more specialized body types, earlier than researchers suspected.
鈥淟ooking at the first few geologic minutes of the Puercan is key to understanding the evolution of mammals over the millions of years that followed, including the origin of today鈥檚 orders of mammals,鈥� Eberle said.
