In the geologic timescale, the Callovianis an age or stage in the Middle Jurassic, lasting between 166.1 ± 4.0Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian.[1]
An example of a Callovian dinosaur Omeisaurus.