Complex sentence: The Tonian (from Greek τόνος "(tónos)", meaning "stretch") is the first geologic period in the Neoproterozoic Era and lasted from Mya to Mya (million years ago).
Split into simpler sentences: The Tonian (from Greek τόνος "(tónos)", meaning "stretch") is the first geologic period in the Neoproterozoic Era. It lasted from Mya to Mya (million years ago).