A researcher from the University of Arizona is part of an international team that has discovered the earliest known complete nervous system.

The fossil is about three centimeters long, and more than a half a billion years old. It was once an ocean dwelling creature with two pairs of eyes and a large claw.

It’s density allowed researchers to use imaging technology to analyze it.

Nicholas Strausfeld, a UA professor and member of the international team that found the specimen, said it's a distant relative of spiders and scorpions.

“The exciting find is that we have a nervous system that looks like a modern nervous system but it’ terms of body organization, a very simple form of an arthropod that lived so long ago," he said.

Strausfeld said the fossil’s nervous system is similar to a modern horseshoe crab.

The specimen was found in a rock outcropping in southwest China.