An illustration provided by the University of Arizona shows the similarity between the brain of a living velvet worm, left, and the fossilized brain of an ancient animal. (Reuters)

Researchers writing in the journal Nature last week described fossilized remains showing the brain structures of a bizarre group of sea creatures that were the top predators more than half a billion years ago.

The fossils, unearthed in China, show an animal, Lyrarapax unguispinus, that lived during the Cambrian Period, when many major animal groups first appeared. It was a member of a group known as anomalocaridids — primitive relatives of arthropods, which include crustaceans, insects and spiders — that hunted prey with a pair of clawlike grasping appendages in front of the eyes.

Anomalocaridids do not have any direct descendants alive today, but the brain structures of Lyrarapax closely resemble those of velvet worms, wormlike animals that crawl along the ground in tropical and semitropical forests in the Southern Hemisphere.

Velvet worms, also known as onychophorans, grow to a few inches in length, have two long feelers extending from the head and have numerous pairs of stubby, unjointed tubular legs that each end in a pair of small claws.

Lyrarapax, whose scientific name means “spiny-clawed, lyre-shaped predator,” lived 520 million years ago. Its neuroanatomy resembles that of velvet worms in multiple ways, with a simple brain and a pair of ganglia — a cluster of nerve cells — placed in the front of the optic nerve and the base of the grasping appendages.