trilobites

• Planktonic trilobite are small and float. They have small eyes or no eyes because they don’t need to see. They have a light weight exoskeleton. Cephalon and pygidium are both the same size for balance. They have a very small thorax with only one or two pleura because its not able to move. 
• Infuanal burrower trilobites have no eyes because they do not need to see, they have a  pitted head shield. They have long genal spines to propel them into sediment. 
• Epifaunal trilobites have eyes on top of their heads suggesting floor dweller. Large genal spines for support in soft sediment. They have lots of pleura for walking. 
• Infuanal shallow burrowers. are small and streamlined. Their eyes are found on top of stalks that face upwards and were level with the sea bed.
• Shallow water epifaunal have eyes on turrets with a lip on top which acted like a sunshade, suggesting they were active during the day. 
• Walliserops trilobites had three pronged tridents on their cephalons. Function remain uncertain   
• Trilobites are extinct so we cannot use the principle of uniformitarianism to research them. 
• Horseshoe crabs are the closest living relative of the trilobites. 
• Many trilobites could curl into a ball to protect themselves, Or they evolved long spines.