A revision of the genus in 2009 provided a differential diagnosis, a list of traits in which "Saurornithoides" differed from certain relevant relatives, especially concentrating on determining its place in the evolutionary tree. That "Saurornithoides mongoliensis" might be more derived, higher in the tree, than "Sinornithoides" and "Sinusonasus", is indicated by the lack of a "fenestra promaxillaris", a small opening at the front side of the snout, and the possession of large denticles on the rear tooth edges as well as the presence of the high number of six sacral vertebrae. That "S. mongoliensis" might be more basal, lower in the tree, than "Zanabazar" and "Troodon", is shown by the presence of a "recessus tympanicus dorsalis", the upper one of three small openings on the side of the braincase, in the inner ear region.