Trilobites are arthropods belonging to the class Trilobita within the phylum Arthropoda. Their bodies are divided into three distinct segments: the head, thorax, and abdomen. A hard exoskeleton covers their dorsal surface, with the shell longitudinally segmented into three lobes. The head is protected by a robust carapace known as the cephalon; the centrally raised portion of the cephalon is called the glabella, whose shape and size vary significantly depending on the species. The anterior part of the glabella is the cranial shield, which bears the eyes; the abdomen and tail are likewise encased in a protective exoskeleton.