They have 24 eyes arranged in four clusters; 16 are simply light-sensitive pits, but one pair in each cluster is complex, with a sophisticated lens, retina, iris and cornea. Trilobites went down a ...

More than 22,000 species of trilobite have been named. This is largely because the trilobite exoskeleton was made of a mineral called calcite, which fossilized very easily. However, fossils ...