Research press release




スカンソリオプテリクス類は、小型恐竜(体重約200グラム)の分類群で、前肢と指が非常に長く、樹上生活する羽毛恐竜として復元されるのが一般的だ。しかし、最近発見されたスカンソリオプテリクス類恐竜のYi qi は、これとは異なっていた。イー(Yi qi)には、尖筆状突起(styliform element)に支えられた、コウモリの翼に似た膜状翼があったと考えられるのだ。この種の膜状翼は、恐竜以外の飛行能力を有する脊椎動物の系統(コウモリ類や翼竜類など)が持っていたが、獣脚類恐竜も有していたことはこれまで知られていなかった。

今回、Min Wangたちの研究グループは、Ambopteryx longibrachiumと名付けたスカンソリオプテリクス類について、これがイーと同じような膜状翼と尖筆状突起を有していたと説明している。しかし、Ambopteryxにはイーと異なる特徴がいくつかあり、例えば、Ambopteryxは前肢骨の幅が広く、短い尾の末端で椎骨が融合しており、非常に長い前肢は後肢より長い。


The fossil of a newly discovered species of scansoriopterygid dinosaur with bat-like wings, found in Liaoning Province, China, is described in a paper published this week in Nature. This specimen, dated to around 163 million years ago, provides further evidence that suggests that dinosaurs closely related to birds experimented with different wing structures near the origins of flight.

The scansoriopterygids form a group of tiny dinosaurs (around 200 grams) that are generally reconstructed as feathered tree climbers, with very long hands and fingers. However, the recently discovered scansoriopterygid dinosaur Yi qi was different. In addition to feathers, Y. qi had what appeared to be bat-like, membrane wings supported by a styliform - a long, pointed wrist bone. This type of membranous wing has been used by lineages of non-dinosaur flying vertebrates such as bats and pterosaurs, but was previously unknown among the theropod dinosaurs.

Min Wang and colleagues describe a scansoriopterygid named Ambopteryx longibrachium, which has membranous wings and a styliform, similar to Y. qi. However, several features distinguish Ambopteryx from its cousin, including a wider forelimb bone, a short tail ending in fused vertebrae and an elongated forelimb that is longer than the hindlimb.

The authors show that marked changes in wing structure evolved near the split between scansoriopterygids and the bird lineages, as the two underwent different paths to becoming airborne. They suggest that the membranous wings and elongated forelimbs present in scansoriopterygids probably represent a short-lived experimentation with flight, which occurred before the later predominance of feathered wings.

doi: 10.1038/s41586-019-1137-z

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