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Sea life recovered from Permian mass extinction faster than we thought

An exceptional assemblage of marine fossils from China seems to show that life in the oceans recovered surprisingly quickly after the biggest mass extinction in Earth’s history.

The so-called Great Dying at the end of the Permian Period around 252 million years ago is thought to have been brought about by unusually high volcanic activity that led to ocean acidification and global warming. The disaster was particularly hard on marine life, wiping out more than 80 per cent of life in the oceans.

For a long time, palaeontologists believed that it took around 8 million years for ocean ecosystems to recover from this setback and evolve into the modern form we know today.

Haijun Song at the China University of Geosciences in Wuhan and his colleagues studied the Guiyang Biota, an exceptionally well-preserved group of marine fossils in southern China dating from 251 million years ago, at the start of the Triassic Period. It includes at least 40 different species of fish, clams, ammonites and crustaceans like shrimps and lobsters.

The fossils include representatives of all levels of the food chain, from 1-metre-long predatory coelacanths to tiny, single-celled amoebas. While some major groups of organisms made it through the mass extinction, many others that had been abundant before, such as the trilobites, were lost.

The collection of species looks much like what we see in modern oceans, says Song, apart from the ammonites, which had the bad luck to go extinct along with the dinosaurs at the end of the Cretaceous. This suggests that there was an unexpectedly diverse and complex marine ecosystem in place just 1 million years after the Great Dying. “In geological history, that’s rapid,” he says.

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Paul Wignall at the University of Leeds, UK, says this fossil collection is full of exciting new discoveries, especially the shrimp and lobster, which hadn’t been seen in the Early Triassic before. But he thinks that the study’s authors are overstating the speed of the recovery. While there are lots of different fish, the diversity of species on the seafloor is still rather modest, with some way to go before it would reach modern levels of diversity, he says.

David Bottjer at the University of Southern California, Los Angeles, also says that the fossils show an ecosystem still in an early phase of its recovery. “There’s a diversity of things being done in the ecosystem, but they’re being done by a skeleton crew,” he says.

Taken together with other fossil records, Bottjer says this shows that the recovery was probably patchy, with marine communities in some parts of the world recovering more quickly than in others. “It’s the same thing we see in today’s environmental crises,” he says. “Some places are affected more than others.”

Science DOI: 10.1126/science.adf1622

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