Mesozoic that would move into their current positions during the next era. The climate of the Mesozoic was varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. Dinosaurs appeared in the Late Triassic and became the dominant terrestrial vertebrates early in the Jurassic, occupying this position for about 135 million years until their demise at the end of the Cretaceous. Birds first appeared in the Jurassic, having evolved from a branch of theropod dinosaurs. The first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg (33 lb)—until the Cenozoic.
The Age of Reptiles the mural's beginning to the end of the Cretaceous period, 65 million years ago. Each period's length on the mural is proportional to the period's length in geologic time. Each period of time is divided by large trees in the foreground. Animal species are in bold. Devonian Carboniferous Permian Triassic Jurassic Cretaceous "The Age of Reptiles" won Zallinger several awards. Zallinger was awarded with a Pulitzer Fellowship in Art in 1949, and the painting was featured as a postage stamp in 1970. Despite its somewhat outdated view of dinosaurs, "The Age of Reptiles" is still notable for its historical and