4.2.3 Erathem (Eratem)
4.2.3.1 The erathem is the formal chronostratigraphical unit ranking next below an eonothem. It consists of several adjacent systems. The names of the three Phanerozoic erathems are based on early views about stages in the development of life on Earth: Palaeozoic (old), Mesozoic (intermediate) and Cenozoic (recent) life. Several names have been proposed for Precambrian erathems, but none are officially recommended; they are still being considered by the IUGS Subcommission on Precambrian Stratigraphy. The division of time corresponding to an erathem is an era (æra).