1. Limbs (Arms and Legs): The limbs of vertebrates are modified appendages used for walking, running, climbing, flying, swimming, and various other forms of locomotion. Limbs consist of bones, joints, and muscles that work together to generate movement.
2. Wings: In birds and bats, the forelimbs are modified to serve as wings, enabling them to fly. Wings consist of a framework of bones covered with skin and feathers or membranes.
3. Fins: Aquatic vertebrates like fish and some marine mammals have fins, which are limb-like structures used for swimming. Fins consist of various bones, fin rays, and connective tissue that provide support and aid in propulsion through the water.
4. Flippers: Certain aquatic mammals, such as whales, dolphins, seals, and sea lions, have flippers. Flippers are modified forelimbs or hind limbs used for swimming and are typically flattened, paddle-like structures.
5. Digits: Digits are the individual finger- or toe-like structures at the distal end of the limbs. They consist of bones called phalanges and provide additional grasping and manipulative capabilities.
6. Pelvic and Pectoral Girdles: The pelvic and pectoral girdles are skeletal structures that connect the appendages to the axial skeleton (vertebrae and ribs). The pectoral girdle supports the forelimbs, while the pelvic girdle supports the hind limbs.
These skeletal structures, along with their associated musculature, nerves, and other tissues, form the appendicular skeleton. The appendicular skeleton is crucial for vertebrate mobility, dexterity, and diverse adaptations to different environments.