Concepts and Controversy

Active or Passive Fliers Page 2. The skeleton provides indirect evidence on the size of the flight muscles; scars are left on the bone where the muscles once attached. The size of the scars can be directly correlated to the size of the muscle. The sternum shows huge muscle attachment scars. If Pterosaurs were only capable of gliding then scars should only reflect small flight muscles.

The range of motion that is supported by the shoulder indicates two distinct and separate motions: there is motion in the vertical plane, and a combined motion forward and down. These same degrees of motion are found in birds and bats. The motion in the vertical plane is used in high speed flight while the other degree of motion is used in slow speed flight (predominately takeoff and landing).

The skeletal evidence alone strongly suggests that pterosaurs were very well adapted to life in the air and were very capable active fliers. Even the largest Pterosaurs were capable of sustained flight by flapping their wings. However, it is very likely that the largest pterosaurs had a lifestyle similar to large birds: soaring on thermals.

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