Research press release


Nature Communications

Palaeontology: Palaeozoic sharks survived mass extinction


今から3億5000万年前に大きな生物学的転換が起こり、二畳紀と三畳紀という地質年代の境目になった。この転換は、いくつかの魚分類群、特に軟骨魚類の大量絶滅と現生サメ類の定着をもたらした。今回、Guillaume Guinotたちは、フランス南部の深海底の1億4000万年~1億3300万年前の地層から、いくつかの歯の化石を含むcladodontomorphサメの化石群を発見した。このサメは、二畳紀と三畳紀の境界期に姿を消したと考えられていたが、今回の発見によって、このサメ類の化石記録が約1億2000万年も先まで伸びた。Guinotたちは、このサメが二畳紀末期の大量絶滅を生き延びたことが、この新たな化石によって明らかになったと考えている。


The discovery of ancient cladodontomorph shark fossils in Southern France suggests that these marine creatures survived the end-Permian mass extinction, or Great Dying, when it had been previously thought that they died out. The end-Permian mass extinction is believed to have wiped out over 90% of all marine species and around 70% of terrestrial vertebrate and this finding, published in Nature Communications, suggests that cladodontomorph shark may have survived the event by moving to deep areas of the ocean.

A major biological turnover occurred about 350 million years ago, marking the boundary between the Permian and the Triassic geologic periods. This turnover represents a mass extinction of several fish groups and cartilaginous fishes in particular, and the establishment of modern sharks. Guillaume Guinot and colleagues find a cladodontomorph shark assemblage, including several fossil teeth, in a deep sea platform of Southern France from 140-133 million years ago. Cladodontomorphs were thought to have vanished at the Permian-Triassic boundary but this finding increases the fossil record of the group by about 120 million years. The authors suggest that this shows that the cladodontomorphs survived the end-Permian mass extinction.

The researchers propose that these now extinct sharks survived the Permian-Triassic transition in deep-sea refuges during catastrophic events, and suggest that these findings illustrate how deep-sea fossils contain valuable information about the evolutionary history of ancient fishes.

doi: 10.1038/ncomms3669

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