Most or all pterosaurs had hair-like filaments known as pycnofibers on the head and torso.
The term "pycnofiber", meaning "dense filament", was coined by palaeontologist Alexander Kellner and colleagues in 2009.
Pycnofibers were unique structures similar to, but not homologous (sharing a common origin) with, mammalian hair, an example of convergent evolution.
A fuzzy integument was first reported from a specimen of Scaphognathus crassirostris in 1831 by Georg Augustus Goldfuss, but had been widely doubted.
Since the 1990s, pterosaur finds and histological and ultraviolet examination of pterosaur specimens have provided incontrovertible proof: pterosaurs had pycnofiber coats.
Sordes pilosus (which translates as "hairy demon") and Jeholopterus ninchengensis show pycnofibers on the head and body.

The presence of pycnofibers strongly indicates that pterosaurs were endothermic (warm-blooded).
They aided thermoregulation, as is common in warm-blooded animals who need insulation to prevent excessive heat-loss.
Pycnofibers were flexible, short filaments, about five to seven millimetres long and rather simple in structure with a hollow central canal.
Pterosaur pelts might have been comparable in density to many Mesozoic mammals.
Most or all pterosaurs had hair-like filaments known as pycnofibers on the head and torso. The term "pycnofiber", meaning "dense filament", was coined by palaeontologist Alexander Kellner and colleagues in 2009. Pycnofibers were unique structures similar to, but not homologous (sharing a common origin) with, mammalian hair, an example of convergent evolution. A fuzzy integument was first reported from a specimen of Scaphognathus crassirostris in 1831 by Georg Augustus Goldfuss, but had been widely doubted. Since the 1990s, pterosaur finds and histological and ultraviolet examination of pterosaur specimens have provided incontrovertible proof: pterosaurs had pycnofiber coats. Sordes pilosus (which translates as "hairy demon") and Jeholopterus ninchengensis show pycnofibers on the head and body.
The presence of pycnofibers strongly indicates that pterosaurs were endothermic (warm-blooded). They aided thermoregulation, as is common in warm-blooded animals who need insulation to prevent excessive heat-loss. Pycnofibers were flexible, short filaments, about five to seven millimetres long and rather simple in structure with a hollow central canal. Pterosaur pelts might have been comparable in density to many Mesozoic mammals.
Pterosaur