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Ancient jellyfish ancestor solves an evolutionary mystery

What hid inside the first exoskeletons?

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Many animals couldn’t survive without their exoskeletons.

Insects, spiders, crustaceans, and coral are just some of the creatures that wear their protection on the outside.

But identifying the very first animals with exoskeletons has been a challenge for science.

These hard structures appear suddenly in the fossil record between 550 to 520 million years ago, when the Cambrian Explosion took place.

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However, due to the fact that soft tissues degrade quickly over time, the bodies of these ancient creatures are difficult to identify and place on the evolutionary tree.

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But a group of extremely well-preserved animals unearthed in Yunnan Province, China, give researchers a peek into the lives of some of the first living things with exoskeletons.

Writing last week in the journal Proceedings of the Royal Society B, researchers described four specimens with fossilized tissue and skeletons that date back 514 million years.

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The fossils represent the remains of Gangtoucunia aspera, a tube-like animal that dwelled on the seafloor during the Cambrian Period.

Preserved soft tissue from the new Gangtoucunia fossils revealed that the creatures had a gut and retractable tentacles tucked inside their hard exoskeletons.

Luke Parry and Guangxu Zhang

Here’s a reconstruction of the creature’s anatomy.

Luke Parry and Guangxu Zhang

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Though large groups of fossilized Gangtoucunia skeletons have been found before, researchers haven’t been sure how to classify them.

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The authors of the new study concluded that Gangtoucunia belong to a group of animals called cnidaria, which today includes jellyfish, sea anemones, and corals.

They have distinct similarities to their modern cousins, too.

The tentacles that attached to Gangtoucunia’s mouth were likely used to sting and capture prey, much like today’s jellyfish. Though they would have been stationary creatures, like corals.

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Luke Parry and Guangxu Zhang

Not only do the fossils shed light on an important ancestor to some of today’s sea creatures, but they also help piece together what was beneath the first exoskeletons.

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“This really is a one-in-million discovery. These mysterious tubes are often found in groups of hundreds of individuals, but until now they have been regarded as ‘problematic’ fossils, because we had no way of classifying them.

Thanks to these extraordinary new specimens, a key piece of the evolutionary puzzle has been put firmly in place.”

Luke Parry, study co-author, in a press release