Model of the trilobite, Dipleura lilydalensis.
Image: Rodney Start
Source: Museum Victoria
Fossil of Dipleura lilydalensis
Source: Museum Victoria
A major extinction event at the end of the Ordovician period had a great impact on trilobites and other shallow marine animals. Trilobites recovered somewhat during the Silurian but never again reached the same diversity that they once had. In another series of extinctions in the second half of the Devonian, all but one of the remaining major groups of trilobites disappeared.