Scientists say they've discovered fossilized remains of a new species of one of the world's first known predators, from a distant past when all life on Earth was in its oceans.

The 500-million-year-old creature from the Cambrian Period, known as an anomalocaridid, was unearthed in China, and the fossil is preserved so well that parts of the nervous system and brain are clearly discernable, the researchers say.

Anomalocaridids -- the name means "abnormal shrimp" -- was a fierce-looking arthropod possessing compound eyes, an armored body, and spiked claws to capture and hold prey.

The brain of the new species, dubbed Lyrarapax unguispinus, "spiny-clawed lyre-shaped predator," has helped settle a long dispute about where anomalocaridids should be placed in the tree of life.

"Our discovery helps to clarify this debate," says University of Arizona scientist Nicholas Strausfeld. "It turns out the top predator of the Cambrian had a brain that was much less complex than that of some of its possible prey and that looked surprisingly similar to a modern group of rather modest worm-like animals."

The fossilized brain suggests the ancient animal belonged on a branching of the animal kingdom whose living examples today include a creature known as a velvet worm, a small predator with short unjointed legs and a pair of small claws.

Velvet worms, also known as onychophorans, possess a simple brain situated in front of their mouth and a bundle of nerve cells positioned in the front of their optic nerves at the base of long feelers.

"And -- surprise, surprise -- that is what we also found in our fossil," Strausfeld says, citing the pair of grasping claws in front of the eyes of the anomocaridid.

What sets the anomalocaridids apart from their modern-day relatives is size. Velvet worms are just a few inches in length; anomalocaridids could grow as large as 6 feet long.

The fossil examples unearthed of the new species were just 6 inches long, but may have been young and growing, researchers say.

"The three known specimens may represent immature stages of the animal, so it might be larger," says study co-author Peiyun Cong of Yunnan University, who uncovered the Lyrarapax fossils in 2013.

The brains of anomalocaridids -- simple yet apparently well suited to the task of locating and capturing prey -- may helped drive the evolution of complex brains in those prey species, Strausfield suggests.

"With the evolution of dedicated and highly efficient predators, the pressure was on other animals to be able to detect and recognize potential danger and rapidly coordinate escape movements," he says. "These requirements may have driven the evolution of more complex brain circuitry."

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