A few teeth, smaller than a grain of rice, are changing the map of your earliest primate relatives. They come from a creature called Purgatorius, a tiny tree-dwelling mammal that lived about 66 million years ago, right after the dinosaurs vanished. For decades, fossils of this animal turned up only in northern places like Montana and Saskatchewan. That left a big blank space farther south, where some scientists suspected Purgatorius simply was not there. Now, that blank space has a dot. A team led by paleontologist Stephen Chester, an anthropology professor at the CUNY Graduate Center and Brooklyn College, reports the southernmost Purgatorius fossils ever found. They were recovered from Colorado’s Denver Basin, at the Corral Bluffs study area. The work appears as the cover article in the Journal of Vertebrate Paleontology, with co-authors Jordan Crowell, Tyler Lyson, and David Krause of the Denver Museum of Nature & Science. A lifelike rendering of the archaic primate Purgatorius. (CREDIT: Andrey Atuchin.) The teeth that moved the boundary The new specimens are not skulls or skeletons. They …