Trilobite – meaning “three lobes” – refers to an extinct class of marine arthropods. The arthropod family included invertebrate animals with an exoskeletons and a segmented body. Lichida in particular are known for their elaborate and pronounced spines used as a defence mechanism to warn off predators. They usually have between eight to thirteen segments. Trilobites became extinct around 250 million years ago, in the late Permian period. This was during the Permian-Triassic extinction event – which is thought to have been caused by ocean acidification. Many other species – like Gonitatie Ammonites – disappeared in this event, often referred to as the ‘Great Dying’.