Feathers were once considered to be unique avialan structures linked to birds evolutionary success. Primitive theropods, such as Sinosauropteryx and the tyrannosaurs Dilong and Yutyrannus, and some plant-eating ornithischian dinosaurs, such as Tianyulong, and Kulindadromeus are known from their spectacularly preserved fossils covered in simple, hair-like filaments called ‘protofeathers’. Other integumentary filaments, termed pycnofibres, has been reported in several pterosaur specimens. The discovery of integumentary structures in other pterosaurs, such as Pterorhynchus wellnhoferi (a rhamphorhynchoid pterosaur), and other exquisitely preserved specimens from China, suggest that all Avemetatarsalia (the wide clade that includes dinosaurs, pterosaurs and close relatives) were ancestrally feathered.
A new specimen of an adult Tupandactylus imperator, a tapejarid pterosaur from north-eastern Brazil, preserves extensive soft tissues which provides more evidence that pterosaurs had feathers. The fossil, originally poached from an undetermined outcrop of the Early Cretaceous Crato Formation, was in privated hands for an unknown period of time and later deposited at the Royal Belgian Institute of Natural Sciences (RBINS). The fossil was repatriated to Brazil early this year.
The new specimen (MCT.R.1884) comprises the posterior portion of the cranium and the remains of a soft tissue cranial crest preserved on five separate slabs. Two types of fibrous integumentary structures were present. The monofilaments (approximately 30 mm long and 60–90 μm wide) resemble those present in the anurognathid Jeholopterus ningchengensis and the ornithischian dinosaur Tianyulong. The most striking feature is the presence of fossil melanosomes with diverse morphologies that supports the hypothesis that the branched integumentary structures in pterosaurs are feathers.
Melanosomes are granules of the pigment melanin. The diverse shape of the melanosomes recovered from the skin fibres in the crest, monofilaments and branched feathers resembles that in the skin of extant birds and mammals. This is an indication that pterosaurs had the genetic machinery to control the colors of their feathers.
Cincotta, A., Nicolaï, M., Campos, H.B.N. et al. Pterosaur melanosomes support signalling functions for early feathers. Nature (2022). https://doi.org/10.1038/s41586-022-04622-3