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. 2006 Mar 7;273(1593):1563–1568. doi: 10.1098/rspb.2006.3489

Figure 2.

Figure 2

Evolution of walking (W) and running (R) locomotor mechanics in tetrapods. Grey bars indicate the earliest known appearance of animals considered morphologically similar to extant forms (Estes & Rieg 1973; Rest et al. 2003; Gao & Shubin 2001; Parchman et al. 2003; Ji et al. 2002). Nodes indicate estimated divergence times of the major tetrapod groups (Rest et al. 2003). Mechanical patterns of COM movements known for extant forms (Cavagna et al. 1977; Farley & Ko 1997; Ahn et al. 2004; Willey et al. 2004; figure 1) are mapped as walking, W (out-of-phase kinetic and potential energy, and running, R (in-phase kinetic and potential energy), and parsimony was used to infer nodal character states (W&R). R?, running mechanics assumed based on galloping gait in crocodilians (Renous et al. 2002).