Research press release


Nature Communications

Palaeontology: Oldest fossilised snakes found


今回、Michael Caldwellたちは、英国、ポルトガル、米国で発見されたヘビの頭蓋骨の化石を用いて1億6700~1億4300万年前に生息していたヘビの新種(4種)を同定し、最初期のヘビが出現した時期には、有鱗爬虫類の他の主要な分類群の大部分が急速に多様化していたこと、そして、これらのヘビは、ジュラ紀中期に世界各地のさまざまな生息地(沼地、池、河川、沿岸系など)に存在していたことを明らかにした。


The oldest known snake fossils ever discovered are described online in Nature Communications this week. The fossils push back the first record of snakes by 70 million years and challenge previous theories that suggested that the snake’s head evolved after the evolution of its elongated body.

Using a number of fossilised skull bones, Michael Caldwell and colleagues identified four new species of snakes, from England, Portugal and the USA, dating from 143 to 167 million years ago. They find that snakes originated at a time when most other major groups of scaled reptiles were rapidly diversifying and that they existed in different parts of the globe in many different habitats including swamps, ponds, rivers and coastal systems, during the Middle Jurassic.

The creatures share recognisable features with modern-day snakes, such as sharp, backward pointing teeth, but their overall shape, length and body form remains unknown. The authors suggest that the presence of key snake-like features in these early snake skull bones hints that the classic snake head evolved first and was then followed by the evolution of the elongated, limbless body.

doi: 10.1038/ncomms6996

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