古生物学：翼竜の羽毛にも色彩パターンがあり得た

Some pterosaurs possessed feathers with varied pigmentation that were used for both thermoregulation and display, a Nature study suggests. The finds shed light on the early evolutionary history of feathers.

It is known that pterosaurs had fluffy coats consisting of hair-like fibres called pycnofibres, but whether or not these structures were true feathers has been debated. In this study, Maria McNamara, Aude Cincotta and colleagues analysed the partial skull of Tupandactylus imperator, a pterosaur from the Early Cretaceous of Brazil (dated to approximately 113 million years ago). Two types of feathers were observed on the cranial crest; smaller, unbranched monofilaments, and larger, branching structures that are more like modern-day bird feathers.

With the soft tissue well preserved, the team were able to examine the fine detail of pigment-producing structures known as melanosomes. Different types of melanosomes were identified in both feathers and skin, a feature previously known only from theropod dinosaurs and extant birds. This suggests that the melanosomes provided the feathers with colour, just like they do for birds today. Taken together, the finds hint that, although these feathers may not have been used for flight, they were being used as a form of visual communication, and that the genetic mechanisms underpinning this ability were already in place in early-diverging reptiles in the Middle to Late Triassic (around 247 to 201 million years ago).