hemera
noun
hem·era
ˈhemərə
plural hemerae
-ə(ˌ)rē
also hemera 1
: a stratigraphic zone comprising the time range of a particular fossil species
2
: a period of time during which a race of organisms is at the apex of its evolution
Word History
Etymology
New Latin, from Greek hēmera day; akin to Greek ēmar day, Armenian aur