Plantigrady

Plantigrady is a form of terrestrial locomotion in which the animal bears weight on the entire underside of the foot, including the heel and toes, with the sole in contact with the ground during stance. The term comes from Latin planta (sole) and gradi (to walk). This posture contrasts with digitigrady, where weight is carried on the toes, and with unguligrady, where weight is borne on the tips of shortened digits (hooves).

In many mammals, plantigrade locomotion provides stability and balance, especially on uneven terrain or when manipulating objects with the feet. It generally results in slower movement than digitigrade or unguligrade gait but enhances ground contact, traction, and the ability to grip or climb. The hind foot and ankle often show greater mobility to accommodate varied surfaces, and foot pads or claws can aid shock absorption and control.

Distribution and examples: Plantigrade postures are found in humans and other primates, as well as bears, raccoons, beavers, otters, and many rodents. The arrangement supports diverse lifestyles, including climbing, foraging, and manipulating the environment.

Evolution and comparison: Plantigrady is considered primitive in mammalian evolution, with digitigrade and unguligrade postures evolving in several lineages to improve running speed and efficiency. Modern humans retain a plantigrade stance while adapting the foot for upright bipedal locomotion, balance, and energy storage through the arch.