For a long time it has been known that some pterosaurs have hair. This has been seen as pycnofibers in some fossils. It is only with the advent of better quality fossils and improved techniques that the nature of these hairs is being better understood. This is documented in the following paper:
Yang Z., Jiang B., McNamara M. E., Kearnes S. L., Pittman M., Kaye T. G., Orr P. J., Xu X. and Benton M. J., 2019, Pterosaur integumentary structures with complex feather-like branching, Nature Ecology & Evolution, 2018; 3 (1): 24
There appears to be 4 types of hair like fibres found in pterosaur specimens of Anurognathus, Sordes, Jeholopterus and Pterorhynchus. It is probable that these fibres are found in many more pterosaur Genus groups. They are similar to feathery structures seen on some dinosaurs.
Type 1 - Pycnofibers. These are seen in abundance on Sordes Pilosis and have been documented before by
Bakhurina and Unwin. These are seen to be hollow stemmed hair like fibres which are now known to contain melanosomes which are chemically similar to red and black pigment melanosomes and would probably have given a brown colouration to the fibres.
Type 2 and 3 - Radially symmetrical branching fibres. These are found on the head, neck and limbs of the sampled pterosaurs and may be associated with airflow dynamics or thermal insulation.
Type 4 - Bilaterally branching wing fibres. These feather like fibres are found across the wing membranes and are similar to some dinosaur feather structures, suggesting a distant common ancestor. This wing membrane association could be involved with insulation or thermoregulation.
When I see structures like this, I look to the function of wing contour feathers in birds. It is likely that these feathered structures may also have been sensory, giving information about airflow over the flying surfaces to warn of stall limits and variable pressures on those surfaces.
This work is an important enhancement of current knowledge about pterosaur biology and shows more detail about these advanced flyers.
These structures are seen as compacted masses of hair like mats on suitably well preserved fossils. Extracting information about single hairs is quite an achievement.
