Pterosaur melanosomes support signalling functions for early feathers

Remarkably well-preserved soft tissues in Mesozoic fossils have yielded substantial insights into the evolution of feathers(1). New evidence of branched feathers in pterosaurs suggests that feathers originated in the avemetatarsalian ancestor of pterosaurs and dinosaurs in the Early Triassic(2), but the homology of these pterosaur structures with feathers is controversial(3,4). Reports of pterosaur feathers with homogeneous ovoid melanosome geometries(2,5) suggest that they exhibited limited variation in colour, supporting hypotheses that early feathers functioned primarily in thermoregulation(6). Here we report the presence of diverse melanosome geometries in the skin and simple and branched feathers of a tapejarid pterosaur from the Early Cretaceous found in Brazil. The melanosomes form distinct populations in different feather types and the skin, a feature previously known only in theropod dinosaurs, including birds. These tissue-specific melanosome geometries in pterosaurs indicate that manipulation of feather colour-and thus functions of feathers in visual communication-has deep evolutionary origins. These features show that genetic regulation of melanosome chemistry and shape(7-9) was active early in feather evolution.

Automated summary

The study on well-preserved soft tissues in Mesozoic fossils provides valuable insights into the evolution of feathers. Recent research on pterosaurs reveals the presence of branched feathers, suggesting that feathers originated in the ancestor of pterosaurs and dinosaurs in the Early Triassic. However, the homology between pterosaur structures and feathers is still debated. Furthermore, diverse melanosome geometries related to the skin and feathers have been found in pterosaurs, indicating the early genetic regulation of feather color and shape, which has deep evolutionary origins.