Greek ēōs ‘dawn’ and Eocene + Opuntia, called by Chaney “the dawn cactus of the Eocene”. A fossil plant originally thought to be an Opuntia-like cactus, but now considered a member of the family Cyperaceae. Sometimes incorrectly called Euopuntia (Greek eu- ‘true’).
Image credit: Chaney, R.W. (1944). A fossil cactus from the Eocene of Utah. American Journal of Botany 31(8): 507-528.
Maarten H.J. van der Meer (2022 Feb 05). Eopuntia. Dictionary of Cactus Names. Retrieved from https://www.cactusnames.org/eopuntia