Dicellocephalus Minnesotenis a Trilobite
Trilobites ("three-lobes") are extinct marine arthropods that form the class Trilobita. Why the trilobites became extinct is not clear. Their numbers began to decrease with the appearance of the first sharks and other early gnathostomes (jawed vertebrates) in the Silurian and their subsequent rise in diversity during the Devonian period. Trilobites may have provided a rich source of food for these new animals. Fossilised trilobites are often found enrolled (curled up) like modern woodlice for protection; evidence suggests enrollment helped protect against exploitation of arthropod cuticle weakness by Anomalocarid predator attacks.