Eopuntia douglassii Chaney
Eocene
Green River Formation
Bonanza
Montana, USA.

Eopuntia is considered an early relative of modern Opuntia, prickly pear cacti, preserving characteristic pad like morphology and cactus tissue impressions rarely seen in the fossil record. Fossil cacti are exceptionally uncommon because succulent tissues typically decay rapidly before fossilization.
120mm example of the oldest klnown cactus on 215mm slab