B. jaffei was an extremely lightly built and agile animal with big eyes and relative big brains during the Campanian two were entombed in Mongolian sand dunes. One of the dino specimens was found in 1993 at Ukhaa Tolgod, a rich deposit of fossils in southern Mongolia, a second was unearthed nearby three years later. Included among the remains is a good skull. It is the first troodontid known to have unserrated teeth, like those of birds. B. jaffei itself cannot be an ancestor of birds, which evolved some 70 million years earlier, but could have shared a common ancestor with them.

Like its North American reletive, Troodon formosus,  Byronosaurus jaffei was a predator of small animals.  Its large, forward-facing eyes gave B. jaffei a sterioscopic view.  Unlike other troodonts, however, B. jaffei has a large and sensetive nose,  the new dinosaur possesses two birdlike features: teeth that lack steak-knife-like serrations and a chamber in the snout where air enters from the nostrils before passing through to the mouth. Among dinosaurs, troodontids also had large brains relative to their size, approaching the brain-to-size ratio of birds.