Pterosaur melanosomes support signalling functions for early feathers

Abstract

Remarkably well-preserved soft tissues in Mesozoic fossils have yielded substantial insights into the evolution of feathers1. New evidence of branched feathers in pterosaurs suggests that feathers originated in the avemetatarsalian ancestor of pterosaurs and dinosaurs in the Early Triassic2, but the homology of these pterosaur structures with feathers is controversial3,4. Reports of pterosaur feathers with homogeneous ovoid melanosome geometries2,5 suggest that they exhibited limited variation in colour, supporting hypotheses that early feathers functioned primarily in thermoregulation6. 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 shape7–9 was active early in feather evolution.

Locomotion and the early Mesozoic success of Archosauromorpha

“…The success of dinosaurs has been explained by the suggestion that they were endothermic and the pseudosuchians were not [22,23], and this might have been enhanced by the likelihood that dinosaurs and pterosaurs in the Triassic had some form of insulating feathers [8,115,116]. However, there is evidence that both archosaur lineages exhibited endothermy through much of the Triassic, based on their bone histology, inferred red blood cell size, bone pneumaticity, and other characteristics [8,[117][118][119][120].…”

Forged soft tissues revealed in the oldest fossil reptile from the early Permian of the Alps

“…Scale bars represent: 100 μm (A); 50 μm (B). Lindgren et al 2012;Rossi et al 2019Rossi et al , 2020Rossi et al , 2022Yang et al 2019;Cincotta et al 2022), but in some rare cases, melanosomes are not physically preserved. In these cases, the C-rich soft tissue remains appear as an amorphous layer, but a melanin chemical signature can still be found (Brown et al 2017;Fabbri et al 2020).…”

Triassic Revolution

“…Pterosaurs, the sister group of dinosaurs, also have dermal insulating structures commonly called pycnofibres. New evidence (Yang et al, 2019;Cincotta et al, 2022) shows these pycnofibres take a variety of forms, including branching and tufting structures as seen among dinosaurs and birds (Figures 5B,C), so these are presumably also feathers. However, even if researchers balk at calling pycnofibres feathers, it does not change the fact that insulating dermal structures appeared in the first dinosaurs and the first pterosaurs, and the shared ancestry of these two clades is dated to the Early or early Middle Triassic.…”