What are Trilobites?
Trilobites are an extinct group of arthropods (jointed-legged animals) known from more than 10,000 fossil species. The group Trilobita existed from early in the Cambrian Period (520 million years ago) until the end of the Permian Period (250 million years ago). The name Trilobita is derived from the three (tri-) lobed structure of the exoskeleton, which has a raised central lobe (or axis) and a pair of side lobes, called pleurae. The trilobite body is also divided lengthwise into three regions or tagmata: a head or cephalon, a middle region (thorax) composed of several to many articulated segments, and a tail plate called a pygidium, which consists of fused segments.
