Final answer:
The keel bone is not found in a bird's thigh; it is part of the sternum where flight muscles attach. The thigh contains the femur. Bird skeletons, including the keel, are specialized for flight with adaptations like hollow, pneumatic bones.
Step-by-step explanation:
The statement that the keel bone is found in a bird's thigh is false. The keel is actually a blade-shaped structure projecting ventrally from the sternum (breastbone), and it is where the powerful flight muscles, such as the pectoralis major and supracoracoideus, attach.
These muscles are crucial for the flapping motion required for flight. The thigh of a bird contains the femur, which is part of the appendicular skeleton, not the keel. Within a bird's lightweight and specialized skeletal structure, the bones involved in flight, such as the sternum with the keel, are adapted to allow for efficient flight.