Location
 North America
 68 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 ten ton ceratopsid dinosaur of the genus Triceratops wanders a Cretaceous forest 68 million years ago in what is today the western United States.

Triceratops is the best known of the Ceratopsids, 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. While no color pigmentation has been preserved in the fossil remains of ceratopsids, it's not unreasonable to suggest that they may have been very colorful, like many reptiles and birds today.