"Fossils, which are so valuable in tracing the evolution of bones and organs, cannot help with cells." (Willmer 1970, p.2)
Strother, PK, M Brasier, D Wacey, M Saunders, L Timpe, CH Wellman. 2021. A possible billion-year-old holozoan with differentiated multicellularity. Current Biology 31 (12), P2658-P2665.E2, June 21, 2021.https://doi.org/10.1016/j.cub.2021.03.051
Willmer, E.N., 1970, Cytology and Evolution: London, Academic Press, Inc. (London) Ltd., 1–649 p.