Yinlong was discovered in an upper section of this formation which dates to the Oxfordian stage of the Late Jurassic, or 161.2 to 155.7 million years ago. Most other described ceratopsians are known from the later Cretaceous Period.
Yinlong was found in an upper section of the formation that belongs to the Oxfordian stage of the Late Jurassic period, dating back to between 161.2 and 155.7 million years ago. Most other ceratopsians discovered are from the later Cretaceous era.