Data from: The evolution of locomotor rhythmicity in tetrapods

Differences in rhythmicity (relative variance in cycle period) between mammal, fish, and lizard feeding systems have been hypothesized to be associated with differences in their sensorimotor control systems. We tested this hypothesis by examining whether the locomotion of tachymetabolic tetrapods (birds and mammals) is more rhythmic than that of bradymetabolic tetrapods (lizards, alligators, turtles, salamanders). Species averages of intra-individual coefficients of variation in cycle period were compared while controlling for gait and substrate. Variance in locomotor cycle periods is significantly lower in tachymetabolic than in bradymetabolic animals for data sets that include treadmill locomotion, non-treadmill locomotion, or both. When phylogenetic relationships are taken into account, the non-treadmill analysis and the pooled analyses remain significant, the treadmill analysis becomes nonsignificant (but only marginally). The co-occurrence of relatively high rhythmicity in both feeding and locomotor systems of tachymetabolic tetrapods suggests that the anatomical substrate of rhythmicity is in the motor control system, not in the musculoskeletal components.