Struthiomimus altus (Osborn 1917, Late Cretaceous, 4.3m, AMNH 5339) is one of the ostrich-mimic theropod dinosaurs. In the large reptile tree it is derived from a sister to Compsognathus and basal to the Tyrannosaurus clade, including the four-winged 'bird', Microraptor.
Overall much larger than Compsognathus, Struthiomimus had a relatively smaller and toothless skull. The cervicals were longer, the torso was shorter with fewer vertebrae. Pedal digit 1 is absent. The middle (third) metatarsal was proximally pinched by the second and fourth metatarsals.