ScienceEarly CretaceousMongoliahigh confidence

Zavacephale rinpoche is the oldest known pachycephalosaur, dating to roughly 108 million years ago.

Notes on verification

Confirmed by peer-reviewed Nature publication and corroborated by multiple independent science journalism sources and the corresponding author's institutional press release, all consistent on age (~108 million years) and status as oldest known pachycephalosaur.

Sources