Scientists have identified the earliest primate fossils: tiny ancient teeth from a rat-size creature that suggest our ancient ancestors once lived alongside the dinosaurs

The teeth are 0.08 inches (2 millimeters) long and are from the oldest group of primates, known as plesiadapiforms. They were found in the Fort Union Formation in northeastern Montana in the 1980s, but have now been formally identified in a new study, published Feb. 24 in the journal Royal Society Open Science.