Correlation of forelimb long bone morphology with specific functional adaptations of locomotion

The significance of forelimb morphology has been discussed with a focus on specific morphological aspects; nonetheless, the correlation of overall morphology, including various linear measurements, with respect to ecological preference and adaptation has not been extensively explored, particularly using multiple taxa. We investigated the morphological characteristics of the long bones in the forelimbs of mammalian species and their relationship with specific functional adaptations using 20 linear measurements and 22 terrestrial species from seven orders. Principal component analysis and canonical discriminant analysis showed that the lengths of the humerus, radius, and ulna as well as the distance from the smallest width to the proximal and distal ends, and the deltoid tuberosity length distinguished four adaptations: arboreal, terrestrial, fossorial, and semi-aquatic. Moreover, our findings indicate that the distance from the smallest width to the proximal and distal ends, the deltoid tuberosity length, and the breadth of the distal end of the humerus are crucial in differentiating semi-arboreal, aquatic, and fossorial species.