Trilobita are an extinct group that lived around Permian era (250 mya). These groups of arthropods had segmented body plan without specialization. They also contained paired appendages with their body divided into three sections, head called a cephalon, thorax and pygidium.
- Cephalon is protected by exoskeleton plate called cephalic shield.
- Thorax is composed of identical segments enclosed in a series of plates, which helps in movement.
- Pygidium is the tail end, it is also composed of several of fused plates.