a reconstruction of Callichimaera perplexa.

How did crabs evolve 'crabbiness'? It's complicated.

Two new studies dig into crustaceans' crazy evolutionary history.

This artist's reconstruction depicts the newfound fossil crab Callichimaera perplexa, what may be the strangest crab that ever lived.

Illustration by Oksana Vernygora, University of Alberta

What makes a crab a crab? As it turns out, it's not an easy question to answer: A strange new species of fossil crab and a massive new genetic study shed new light on how the animals evolved.

In a new study in Science Advances, researchers unveil a newfound fossil site in Colombia that was formed some 90 million years ago. The site's astounding level of preservation—tiny shrimps' bodies down to the millimeter—is extremely rare, and only a few such sites have ever been found in the tropics.

The bounty includes dozens of specimens of a bizarre crab unlike anything ever found. Named Callichimaera perplexa—the “puzzling, beautiful chimera”—the crab seems to contain a mashup of traits seen in today's larval and

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