propatagium

Propatagium, or propatagial membrane, is a wing membrane that forms part of the leading edge of the wing in certain flying vertebrates. It is a relatively narrow sheet extending from the shoulder toward the wing, with the exact extent varying among groups. In pterosaurs, the propatagium runs from the shoulder to the wing finger, contributing to the forward edge of the wing. In bats, the propatagium spans from the shoulder to the wrist, lying along the front margin of the wing membrane.

The propatagium is integrated with ligaments and muscles that allow adjustments in wing shape during flight. As a flexible leading-edge element, it influences wing camber, stiffness, and aerodynamic forces, aiding maneuverability, takeoff, and sustained flapping. The structure’s shape and tension can affect overall flight performance and energy expenditure.

In paleontology and comparative anatomy, descriptions of propatagial membranes help infer flight styles and relationships among pterosaurs and bats. Studying this component sheds light on how early flying vertebrates achieved stability and control. The propatagium is part of the broader patagial system that encompasses the various wing membranes in these groups.