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.