元古代 Yuán gǔ dài 🔊 Proterozoic (geological era 2500-540m… + Review this word Meanings Yuán gǔ dài name Proterozoic (geological era 2500-540m years ago) Its characters 元yuányuan (as written)HSK 1古gǔancientHSK 5代dàito be a substitute forHSK 5