Model of the trilobite, Neoasaphus kowalbevskii.
Image: Benjamin Healley
Source: Museum Victoria
Fossil of the trilobite, Neoasaphus kowalbevskii.
Image: Jon Augier
Source: Museum Victoria
Trilobites were at their zenith at the start of the Ordovician with over 60 different families living in a variety of marine environments. The morphological diversity of this group peaked during the Ordovician too – they came in a wide variety of shapes and sizes, and some became powerful swimmers. Neoasaphus probably had good vision thanks to its stalked compound eyes.
After this phase of rapid evolution, the mighty trilobites began to decline, becoming rare by the Carboniferous before complete extinction at the end of the Permian.