nannofossil

[ nan-uh-fos-uh l ]
/ ˌnæn əˈfɒs əl /

noun

any fossil so small that it is near or below the limit of resolution of a light microscope.

Origin of nannofossil

1965–70; nanno- + fossil
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019