Oligocene (adj.)youdaoicibaDictYouDict[Oligocene 词源字典]
1856, "pertaining to the Tertiary period between the Eocene and the Miocene," coined in German (1854) by Heinrich Ernst von Beyrich, from oligo- "small, little, few" + -cene. So called because few modern fossils were found in Oligocene rocks.[Oligocene etymology, Oligocene origin, 英语词源]