Pterosaur wings were formed by bones and membranes of skin and other tissues.
The primary membranes attached to the extremely long fourth finger of each arm and extended along the sides of the body.
Where they ended has been very controversial but since the 1990s a dozen specimens with preserved soft tissue have been found that seem to show they attached to the ankles.
The exact curvature of the trailing edge, however, is still equivocal.

While historically thought of as simple leathery structures composed of skin, research has since shown that the wing membranes of pterosaurs were highly complex dynamic structures suited to an active style of flight.
The outer wings (from the tip to the elbow) were strengthened by closely spaced fibers called actinofibrils.
The actinofibrils themselves consisted of three distinct layers in the wing, forming a crisscross pattern when superimposed on one another.
The function of the actinofibrils is unknown, as is the exact material from which they were made.
Depending on their exact composition (keratin, muscle, elastic structures, etc.),
they may have been stiffening or strengthening agents in the outer part of the wing.
The wing membranes also contained a thin layer of muscle, fibrous tissue, and a unique, complex circulatory system of looping blood vessels.
The combination of actinofibrils and muscle layers may have allowed the animal to adjust the wing slackness and camber.

As shown by cavities in the wing bones of larger species and soft tissue preserved in at least one specimen, some pterosaurs extended their system of respiratory air sacs into the wing membrane.
Pterosaur wings were formed by bones and membranes of skin and other tissues. The primary membranes attached to the extremely long fourth finger of each arm and extended along the sides of the body. Where they ended has been very controversial but since the 1990s a dozen specimens with preserved soft tissue have been found that seem to show they attached to the ankles. The exact curvature of the trailing edge, however, is still equivocal.
While historically thought of as simple leathery structures composed of skin, research has since shown that the wing membranes of pterosaurs were highly complex dynamic structures suited to an active style of flight. The outer wings (from the tip to the elbow) were strengthened by closely spaced fibers called actinofibrils. The actinofibrils themselves consisted of three distinct layers in the wing, forming a crisscross pattern when superimposed on one another. The function of the actinofibrils is unknown, as is the exact material from which they were made. Depending on their exact composition (keratin, muscle, elastic structures, etc.), they may have been stiffening or strengthening agents in the outer part of the wing. The wing membranes also contained a thin layer of muscle, fibrous tissue, and a unique, complex circulatory system of looping blood vessels. The combination of actinofibrils and muscle layers may have allowed the animal to adjust the wing slackness and camber.
As shown by cavities in the wing bones of larger species and soft tissue preserved in at least one specimen, some pterosaurs extended their system of respiratory air sacs into the wing membrane.
Pterosaur