The dark band in this photo (indicated by the arrow) of the Hell Creek Formation in Montana is known as the z-coal, a coal layer that marks the approximate boundary between Cretaceous (below) and Tertiary (above) age rocks. read more
The Mesozoic era, known for its length, spanned from 251.902 million years ago to 66.0 million years ago. Starting at the Early Triassic to the Late Cretaceous. These statistics are based on the latest, 2017 version of the International Chronostratigraphic Chart (Geologic Time Scale) produced by the International Commission on Stratigraphy. read more
Mesozoic means "middle animals," and is the time during which the world fauna changed drastically from that which had been seen in the Paleozoic. Dinosaurs, which are perhaps the most popular organisms of the Mesozoic, evolved in the Triassic, but were not very diverse until the Jurassic. read more