Research press release



翼竜類の一部にはさまざまな色素が沈着した羽毛があり、体温調節とディスプレイ(誇示)の両方に用いられていたことを示唆する論文が、Nature に掲載される。この発見は、羽毛の初期の進化史を明らかにする手掛かりとなる。

翼竜類には、毛状の繊維(ピクノファイバー)でできた綿毛があることが知られているが、これが本物の羽毛かは議論の的になっている。今回、Maria McNamara、Aude Cincottaたちは、白亜紀前期のブラジルに生息していた翼竜類Tupandactylus imperator(約1億1300万年前のものと年代決定された)の頭蓋骨の一部を分析した。頭蓋隆起には、2つのタイプの羽毛が見られ、枝分かれしていない小さな単一フィラメントと、それより大きく、現代の鳥類の羽毛に近い枝分かれ構造のものがあった。


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).

doi: 10.1038/s41586-022-04622-3

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