Palaeontology: Palaeozoic sharks survived mass extinction

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.