"Neither dogs nor bears had evolved when the amphicyonids first appeared about 40 million years ago," says Susumu Tomiya, a vertebrate paleontologist in Chicago, Illinois at The Field Museum of Natural History. The ancestors of the modern-day carnivores were much smaller when they first appeared, but over millions of years, they have evolved to what we see today.
"It is not clear where and when the amphicyonids evolved, but they apparently showed up about forty million years ago and lived in North America, Europe and Asia," added Tomiya. "The new research is an elegant study that uses tools not available to the previous generations of paleontologists." Vertebrate paleontologist Zhe-Xi Luo of the University of Chicago says. The new survey has placed the amphicyonids in a new genus called Angelarctocyo.
These bear dogs died out mysteriously, but their extinction may be attributed to the competition from ancestors as well as the close cousins to dogs and cats. These ancestral predators were specialized and slow; they also had flat feet, which made their survival hard when the ecosystem started becoming hotter and less forested.