(A–F) Foot skeletons of Lower Cretaceous birds from China, in order of decreasing size, with reconstructions to match foot skeleton size, based on anisodactyl tracks of modern perching birds with posterior halluxes. (A–D) Sapeornis chaoyangensis (SI ref.11.), (E) Shenshiornis primita (SI ref.12.) a subjective synonym of S. chaoyangensis, according to SI ref.10. F: Eoconfuciusornis zhengi (SI ref.9). Track accompanying A and B based on a modern crow (genus Corvus), re-scaled to foot skeleton size in (C–F). (G–H) Large and small Cretaceous avian theropod (bird) tracks with halluxes) from Korea: Jindongornipes (G) and Koreanaornis (H) with Minisauripus (I) for comparison. Note that Minisauripus is smaller than all other tracks with relatively thick fleshy digits and low digit divarication angles. All images redrawn by MGL, to same scale, in Adobe photoshop (version CS6 www.adobe.com/Photoshop), with modifications to show digits simplified and separated and obstructive material removed for clarity.