https://www.nature.com/articles/s41559-018-0728-7.epdf?author_access_token=g0SJk_S0UlYkd9ChFUOfsdRgN0jAjWel9jnR3ZoTv0OhuDOmy4G-1OHvOkIfGGVa9hjNadq-O6la97WKFFA-U_CzDuLx5hrx52MRXIaHCxe0wHtP1JSprPoeDcECtIaKGps55q9OlM6xBJamyA2RWA%3D%3D
Pterosaur integumentary structures with complex feather-like branching
Pterosaurs were the first vertebrates to achieve true flapping flight, but in the absence of living representatives, many questions concerning their biology and lifestyle remain unresolved. Pycnofibres—the integumentary coverings of pterosaurs—are particularly enigmatic: although many reconstructions depict fur-like coverings composed of pycnofibres, their affinities and function are not fully understood. Here, we report the preservation in two anurognathid pterosaur specimens of morphologically diverse pycnofibres that show diagnostic features of feathers, including non-vaned grouped filaments and bilaterally branched filaments, hitherto considered unique to maniraptoran dinosaurs, and preserved melanosomes with diverse geometries. These findings could imply that feathers had deep evolutionary origins in ancestral archosaurs, or that these structures arose independently in pterosaurs. The presence of feather-like structures suggests that anurognathids, and potentially other pterosaurs, possessed a dense filamentous covering that probably functioned in thermoregulation, tactile sensing, signalling and aerodynamics.
But there is a disagreement on this:
Dr. Unwin and Professor Martill propose that the branched pycnofibers in pterosaurs are not protofeathers at all, but tough fibers which form part of the internal structure of the pterosaur’s wing membrane, and that the ‘branching’ effect may simply be the result of these fibers decaying and unraveling.
Reply:
https://www.researchgate.net/publication/344413424_Reply_to_No_protofeathers_on_pterosaurs
In our paper1, we explored the morphology, ultrastructure and chemistry of the dermal structures of pterosaurs and showed that they probably had a common evolutionary origin with the integu-mentary structures seen widely in dinosaurs (including birds), their close relatives. Our study of two Middle Jurassic anurognathid pterosaurs from China showed that the whisker-like pycnofibres of the pterosaurs include at least four distinct morphologies, rather than one as had been assumed, and that three of these show branch-ing, a key characteristic of feathers. Further, all four pycnofibre types are morphologically identical to structures already described in birds and non-avialan dinosaurs, not only in terms of gross mor-phology but also in their ultrastructure and chemistry, including melanosomes and chemical evidence for keratin; collectively, these features are consistent with feathers.
