In the last several years, the researchers unearthed three spectacularly preserved specimens of a new species of anomalocaridid in fossil sediments in China. The sediments had frozen these creatures in time so perfectly that the entire nervous system, as well as the gut and some muscles, were still visible.
The creature, dubbed Lyrarapax unguispinus, was about 6 inches (15 centimeters) long.
"The three known specimens may represent immature stages of the animal, so it might be larger," Cong wrote in an email to Live Science.
L. unguispinus had a tail that looked a bit like that of a lobster, and two giant pincers for grasping prey. As it grew, the creature molted, shedding its outer cuticle.
Based on its brain, which lacks some of the characteristic features found in chelicerates, the creature likely shared more similarities with a group known as velvet worms, Cong said.
Still, the new results can't pinpoint where on the tree of life these ancient sea monsters go, Cong said.
But no matter what group they belonged to, by the end of the Paleozoic Era, about 251 million years ago, the last anomalocaridids went extinct, Cong said.
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