What is the main function of the bone that make up pterosaur fingers?

As is the main function of any bone, the main function of the bones in a pterosaur's fingers was to support the finger's structure. Pterosaurs had four fingers on each wing. Three of the fingers stuck out the front of the wing and were used for walking, as pterosaurs were quadrupedal. The extremely elongated fourth finger supported part of the front edge of the wing.