The fossil, which was discovered in the Burgess Shale in Canada, is of a species called Olenoides serratus, which lived around 505 million years ago. It is one of the few known trilobites to have been found preserved in the act of curling up.
The fossil shows that the trilobite began by arching its body upwards, with the front part of the head and tail pointing towards each other. It then gradually folded its body into a ball, with the legs tucked in underneath.
The researchers believe that the trilobite was able to curl up so tightly because of the flexible joints between its body segments. These joints allowed the trilobite to bend its body in a way that would have been impossible for other animals with a more rigid skeleton.
The trilobite's ability to curl up into a ball was likely used as a defence mechanism against predators. By curling up, the trilobite could protect its soft, vulnerable underside from attack.
The researchers believe that the trilobite's ability to curl up may also have helped it to survive in other ways. For example, it may have helped the trilobite to roll away from danger, or to wedge itself into tight spaces.
The fossil is an important addition to our understanding of the behaviour and ecology of trilobites. It provides new insights into how these ancient creatures were able to survive in a harsh environment.
