Joint Angular Excursions and Angular Range Utilization During Stance-Phase Locomotion in Terrestrial Mammals: A Comparative Morphofunctional Data Set

Abstract

Morphofunctional inferences based on anatomical structure often rely on static skeletal features, with limited integration of dynamic locomotor behavior. Although mammalian limb movement exhibits conserved kinematic synergies, to our knowledge no broad comparative data set has quantified how joint poses, angular excursions, and angular range utilization vary across biological factors. A comparative data set of joint motion during the stance phase of walking is presented for 182 terrestrial mammal species spanning 15 orders, classified by limb posture, body mass, top speed, and locomotor habit. Using sagittal-plane video analysis and published sources, joint angles at touchdown, midstance, and toe-off were measured for six major limb joints. From these data, joint angular excursion (JAE), total angular excursion (TAE), and an angular utilization index (AUI% = TAE/∑JAE) expressed as the percentage of summed joint excursion that is realized as net limb excursion during stance, were calculated. Using phylogenetic generalized least squares (PGLS) to account for nonindependence among species, I found that JAE and TAE covaried with the factors considered, with body mass emerging as the dominant predictor. Hindlimb and forelimb TAE decreased with increasing log₁₀ body mass, whereas posture effects were subtle and largely overlapping among categories. Plantigrade, small-bodied and arboreal species tended to display broader angular profiles, whereas unguligrade, cursorial and fast-moving taxa generally used smaller excursions. Quadrant-based comparisons of forelimb and hindlimb AUI further highlighted locomotor strategies aligned with biological factors. Together, these findings indicate that mammals modulate the magnitude and distribution of joint excursions across size and ecological gradients while broadly preserving the proportion of the summed joint excursions range used during stance, providing a reproducible framework for interpreting limb dynamics in extant and extinct mammals.