Quadrupeds

A quadruped is an animal that uses four limbs for locomotion. The term applies to many terrestrial vertebrates, most notably mammals, but also includes some reptiles and amphibians. Quadrupeds are distinguished from bipeds and from animals that move primarily by slithering or hopping.

Anatomy and locomotion: In quadrupeds, all four limbs support the body's weight and contribute to propulsion. Limb posture ranges from plantigrade (the sole placed flat on the ground, as in bears and humans) to digitigrade (walking on toes, as in many carnivorans) and unguligrade (standing on the tips of the hooves, as in horses and deer). The spine, pelvis, and shoulder girdles are adapted to preserve balance and transmit forces during fast or sustained movement. The tail or other body parts may aid balance or steering in some species.

Gaits: Common gaits include walking, trotting, cantering, and galloping, with variations such as pacing or bounding. Gait choice depends on speed, terrain, load, and neuromuscular control. Quadrupeds often coordinate limbs in diagonal pairs (as in trot) or in other patterns to optimize stability and efficiency.

Diversity and role: Quadrupeds range from small rodents to large ungulates and predatory mammals. Many species are domesticated, providing transport, food, companionship, or labor. Evolutionarily, the four-limb body plan enables stable locomotion on varied terrain and under different ecological pressures.