Fossil Find Shows How Life Recovered After 'Great Dying'

Scientists have unearthed a giant trove of nearly 20,000 fossilized reptiles, shellfish and other prehistoric critters, providing a rare glimpse into how life recovered following the planet's most devastating cataclysm.

The ancient marine community was found inside a 50-foot layer of limestone, which today forms part of a hill in Luoping, southwest China.

For the past three years fossil hunters have been chipping away at the rock, excavating the remains of wee beasts, such as crabs, sea urchins and arthropods. And they've also recovered the outsized monsters that ate them, including the first ichthyosaurs -- dolphin-shaped reptiles that grew up to 13 feet long.

This ecosystem started to emerge some 250 million years ago, when south China was a large island floating just north of the equator and life on Earth was almost nonexistent. Around 96 percent of marine species and 70 percent of land vertebrates had been killed off at the end of the previous Permian period, in a mass extinction dubbed "the Great Dying."


Exactly what caused the cataclysm is still not clear. But many scientists suspect that massive volcanic eruptions pumped vast quantities of carbon dioxide and other greenhouse gasses into the air, triggering catastrophic global warming.

The few hardy species that survived the ensuing scarcity of food, wild fluctuations in temperature and shortage of oxygen in the ocean served as the starting point for the recovery of life in the next geologic period, known as the Triassic.

Until now, though, relatively little was known about how life pieced itself back together after the disaster or how long it took for ecosystems to return to a pre-extinction state. (Recovery after most mass extinctions, such as the event that killed off the dinosaurs, typically takes around 1 million to 4 million years.)

This new fossil find has answered some of those mysteries.

Some small marine animals returned fast, according to the study of the Luoping remains, which was published this week in the journal Proceedings of the Royal Society B and authored by paleontologists from China's Chengdu Institute of Geology and Mineral Resources, the University of Western Australia and England's University of Bristol. Nautilus-like ammonoids sprang back to a precataclysm level within 1 to 2 million years, as did snails and bivalves such as clams and oysters.

However, the severity of the wipe-out meant that it took around 10 million years for a fully functioning ecosystem to develop.

By this point, the Luoping fossil record shows that big predators had once again taken their place at the top of the food chain. They include the largest creature the dig team has unearthed so far: a 10-foot-long thalattosaur. This massive marine reptile would have dined on the biggest predatory fish in the sea, which reached lengths of about 3 feet.

Researchers have so far excavated half of the site, and they expect many more finds and breakthroughs to be made over the coming decade. More than half of the fossils discovered so far are completely intact -- meaning their soft tissues have also been fossilized -- as a layer of microbes sealed and protected their bodies when they fell to the ocean floor millions of years ago. The presence of such soft tissue impressions could help paleontologists better understand the creatures' diet and reveal how they evolved and propelled themselves through the water.

"The fossils at Luoping have told us a lot about the recovery and development of marine ecosystems after the end-Permian mass extinction," Mike Benton, a Bristol University paleontologist and a co-author of the study, said in a statement. "There's still more to be discovered there, and we hope to get an even better picture of how life reasserted itself after the most catastrophic global event in the history of our planet."