Location
 Montana, USA
 72 million years ago

Mean atmospheric O₂
 150% of modern level

Mean atmospheric CO₂
 6x pre-industrial level

Mean temperature
 4°C above modern level

A herd of two ton centrosaurine ceratopsian dinosaurs of the genus Einiosaurus roam the plains in what is today the Two Medicine Formation in northwestern Montana. In the distance a long-dormant volcano signals its return to activity by cauterizing snow cover into great clouds of steam. Within weeks the volcano will bury this scene beneath a massive ash fall, preserving the remains of the flora a fauna for future exhumation and examination by Homo sapiens 72 million years later.

Like the better known Triceratops, Einiosaurus was a Ceratopsid, a family of large four-legged plant-eating dinosaurs characterized by beaks, rows of shearing teeth in the back of the jaw, and elaborate horns and frills. While they resemble defensive shields, the frills are in fact relatively fragile, suggesting that they may have served a purpose other than protecting against a brute force attack. One possibility is that the frills were employed as visual displays in order to intimidate rivals and attract the opposite sex.