The Palaeozoic was an Era of Earth history.
Horseshoe crabs were arthropods from the Palaeozoic. (PROSE: The Southwell Park Mermaid)
Martha Jones once thought about how "tomorrow" she could be sightseeing in the Palaeozoic Era. (PROSE: Wishing Well)
Behind the scenes
The Palaeozoic Era contained the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian periods.