Cryptozoon

[ krip-tuh-zoh-on ]
/ ˌkrɪp təˈzoʊ ɒn /

noun

an extinct genus of algae from Precambrian and Cambrian times, forming irregularly hemispherical fossil colonies composed of layers of limy precipitate.

Origin of Cryptozoon

From New Latin, dating back to 1883; see origin at crypto-, -zoon