Figure 2.

Evolution of wrist structure and the radiale angle in tetanuran theropods, based on simplified tetanuran phylogeny after Smith et al. (2007) and Zanno et al. (2009). Numbers indicate values of radiale angle between proximal and distal articular surfaces of radiale, in degrees. Values in bold are direct measurements of individual taxa; values in normal italic type are reconstructed ancestral states. See table 1 and electronic supplementary material, figure S1 for full list of measurements used as the basis for reconstructing ancestral states. Wrist drawings show positions close to zero abduction (Guanlong, Alxasaurus, Deinonychus) or minimum abduction (Caudipteryx, Eoconfuciusornis). II–IV, metacarpals II–IV (numbering convention follows extant birds); d, distal carpal; i, intermedium; R, radius; r, radiale; s, semilunate carpal; U, ulna; u, ulnare. Scale bars: 0.25 cm in Eoconfuciusornis, 0.50 cm in Caudipteryx, 1.00 cm in all other taxa.