Lateral bending of the trunk during terrestrial, quadrupedal locomotion was analyzed in four species of lizards, using high-speed videography and computerized motion analysis. The focus of the analysis was whether lizards produce a standing or a traveling wave of bending in the trunk during locomotion. Lizards with well-developed limbs (Cnemidophorus tigris and Dipsosaurus dorsalis) exhibit a standing wave of lateral bending at low speeds, which is replaced by a traveling wave of bending as velocity increases. Lizards with diminutive limbs (Gerrhonotus kingii and Eumeces multivirgatus) exhibit a traveling wave of lateral bending, even at the lowest speeds recorded. These results are not consistent with the ideas that lizards produce a standing wave of lateral bending during locomotion or that amniote vertebrates have lost the ability to produce a traveling wave of lateral flexion due to a change in the central pattern generator that controls locomotion.

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