"Anchiornis" is a small, early troodontid dinosaur with a triangular skull like other troodontids. Also, "Anchiornis" had long legs, usually an indication of a strong runner. However, the extensive leg feathers indicate that long legs may be an vestigial trait, because running animals tend to have reduced, not increased, hair or feathers on their legs. The forelimbs of "Anchiornis" were also very long, unusual among troodontids (which tend to be short-armed) but similar to dromaeosaurids and early birds, emphasizing its basal ('primitive') position among dinobirds.