中国發現比「始祖鳥」更早鳥化石

Last month the Yomiuri News on-line reported the following

「始祖鳥」よりも原始的な鳥…中国で化石発見

鳥の祖先とされる「始祖鳥」よりも原始的な特徴を持つ新種の鳥の化石を発見したと、ベルギーや中国などの研究チームが３０日付の英科学誌ネイチャーに発表する。

　中国遼寧省の１億６５００万～１億５３００万年前（ジュラ紀中期～後期）の地層から見つかった。研究チームは、「あけぼのの鳥」を意味する「アウロルニス」と名付けた。

　ほぼ全身の化石が見つかり、羽毛の痕跡も確認できた。全長は５１センチ。骨格を分析した結果、始祖鳥よりも恐竜に近く、これまでの鳥の化石のなかで最も原始的であることがわかった。

　鳥は恐竜から進化したと考えられている。ここ数年で羽毛を持つ恐竜が多数見つかったことから、鳥と恐竜の境界があいまいになり、始祖鳥を恐竜と位置づける考え方も出てきた。しかし、始祖鳥よりも原始的な鳥がいたという今回の結果で、「始祖鳥は鳥」という説が改めて有力になった。

（2013年5月30日09時01分 読売新聞）

(試譯文)

The Belgium and China Research teams etc announced to the English science journal ‘Nature’ dated 30th about discovering the fossil of a new species of bird with the feature more primitive than the "archaeopteryx" which so far had been regarded as the ancestor of the bird.

   It was found in China’s Liaoning province at the stratum between165 million and 153 million years ago (the second half of Middle Jurassic). The research teams named it "AURORUNISU" which meant "the bird of dawn."

   Almost the whole body of the fossil was found and the trace of feathers had also been confirmed. The full length was 51 cm. As a result of analyzing the frame, it turned out that it was close to a dinosaur. It was the most primitive bird fossil so far, older than the archaeopteryx.

   It was thought that the bird was evolved from the dinosaur. Since many dinosaurs with feathers were found in the past several years, the boundary of the bird and dinosaur became ambiguous and the view to regard the archaeopteryx as a dinosaur also came out. However, this time because there was a bird more primitive than the archaeopteryx. The theory of "bird Archaeopteryx" has become dominant again

This is an interesting scientific finding. Our understanding of birds could be updated.