The fossil remains found in the drawer of a museum were identified as some of the earliest members of beardog family
Two carnivore fossils that remained hidden in the drawer of a museum for decades have now been identified as the member of a strange extinct group of animals called “bear dogs.” And these fossils of bear dogs can provide more insight into the evolution of canines.
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Discovered in Southwestern Texas, the fossil remains of two small carnivores spent 30 years, inconspicuous and ignored, in the fossil collection of The Field Museum of Natural History in Chicago, Illinois. But when revisited, they turned out to be some of the earliest and elusive members of beardogs family. They have now been reclassified and renamed Gustafsonia and Angelarctocyon.
"We've known about these curious little critters for 30 years, but couldn't tell exactly what kind of carnivores they were.” Lead author Susumu Tomiya, a researcher at The Field Museum said.
The newly classified animals lived 38 to 37 million years ago in what's now Texas and were the size of tiny modern-day dog breed Chihuahua. The finding is surprising because there is no prior evidence that bear dogs inhabited this part of the North America. Moreover, their small sizes are also baffling scientists because some of their decedents were actually large like a bear.
“These are some of the earliest beardogs--they lived 38 to 37 million years ago. By about 15 million years ago, the beardog family had given rise to huge predators bigger than modern lions, but the early members reported in this study were tiny, around the size of a Chihuahua,” said Tomiya.
“There are advantages to being bigger--you can take down bigger prey, you have fewer predators and fewer competing carnivores that can steal your food--but there are disadvantages too. Bigger animals require more food and space, and they reproduce more slowly. Larger animals go extinct at higher rates than smaller animals--recent studies suggest that getting bigger may be a dead-end strategy in mammalian carnivores.”
The new discovery could not have been possible without the keen eyes of the researcher Tomiya who spotted the fossil of a small carnivore while walking through The Field Museum’s collections one day and suspected that it might belong to a very different group of carnivores instead of what it was being called previously. Researchers decided to take a closer look at the specimen alongside another fossil carnivore unearthed from the same area of Texas. After analyzing their subtle features, researchers realized that the animals were likely belonged to beardogs from later time periods. Their idea was later confirmed by the detailed 3D scans of the fossils.
The discovery has broader implications relating to the early evolution of beardogs, suggesting that the region of North American might have played an important role in their evolution.
Bear dogs or amphicyonids are distant relatives of many modern-day animals including dogs, bears, wolves, foxes and sea lions and they can provide important clues on the diversification of dogs in particular.
Tomiya explains. “They're equally related to all of the dog relatives alive today--they're not the direct ancestors of modern wolves and bears, but more like their cousins.”