Trilobites

Trilobites were marine arthropods 521 million years ago and lived for 300 million years until the Permian mass extinction they were usually 1-4 inches long but they could be up to 28 inches for the genus Isotelus rex their closest living relative are horseshoe crabs, and they were most likely hunted by large molluscs which are related to nautilus this is believed because they are frequently found in the same rocks other predators are Cephalopods, Echinoderms, and other large arthropods as trilobites originally the Anomalocaris was believed to eat trilobites but further research suggest they more likely ate soft bodied prey trilobites were primarily scavengers but some of them may have engaged in cannibalism