So here is a summary
The part of the pterosaur wing "closer to the body (the tenopatagium), was extensively covered by elongated and thick fibres here called pycnofibres."
and it was
"A well-developed integumental covering formed by fibres (here named pycnofibres) that are thicker than the actinofibrils"
"The pycnofibres are further formed by smaller fibrils of unknown nature."