Neoproterozoic

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Of, relating to, or being the most recent of the three eras of the Proterozoic Eon, from approximately 1.0 billion to 542 million years ago, marked by the formation of extensive glaciers reaching as far south as the equator and the first appearance of multicellular life.
• noun The Neoproterozoic Era.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective geology Of a geologic era within the Proterozoic eon; comprises the Tonian, Cryogenian and Ediacaran periods from about 1000 to 544 million years ago, when algae and sponges flourished.
• proper noun geology The Neoproterozoic era.