A spectacularly well-preserved sea monster that once prowled the oceans during the Cambrian Period has been unearthed in China.
The 520-million-year-old creature, one of the first predators of its day, sported compound eyes, body armor and two spiky claws for grabbing prey.
The fossils of the new species were so well preserved that the nervous system and parts of the brain were still clearly defined. [Cambrian Creatures: Photos of Primitive Sea Life]
Before the Cambrian Period, which lasted between 543 million and 493 million years ago, most life resembled simple algae and stationary jellyfishlike creatures, but during the Cambrian explosion, a period of rapid evolution when biodiversity exploded, swimming sea creatures with compound eyes, jointed legs and hard exoskeletons emerged.
The period also saw the rise of an iconic group of shrimplike creatures known as anomalocaridids. These ancient sea monsters were the top predators of the Cambrian seas, and sported bladed body armor and a cone-shaped mouth made of concentric plates. Some of the biggest of these bizarre creatures could grow to be up to 6 feet (1.8 meters) long.
But most anomalocaridid specimens paleontologists found have been poorly preserved, making it difficult to know precisely where they fit in the tree of life, said study co-author Peiyun Cong, a researcher at Yunnan University in China.
Some scientists thought anomalocaridids belonged to a group that split off before the most recent common ancestor of all living arthropods, while others thought the animals were part of a group called chelicerates that includes spiders and scorpions. Still others thought anomalocaridids had converged upon similar features to those of modern arthropods but didn't evolve from the same lineage, Cong said in an email.