The Mesozoic Era began around 250 million years ago and ended about 65 million years ago. Both it's beginning and end are marked by major extinction events. The Mesozoic Era is often called the age of the dinosaurs because they were Earth's dominant animals during this era. It's also the era when the first mammals and birds appear in the geologic timeline. T he Mesozoic Era is divided into three periods: the Triassic, the Jurassic, and the Cretaceous. If you haven't already, be sure to check out my other posts about geologic history: Learning About Geologic History- The Paleozoic Era Learning About Geologic History- Fossils Animals of the Mesozoic: Triassic - The end of the previous geological period is marked by a widespread extinction event that resulted in the loss of around 90% of Earth's species. The Triassic Period began with Earth as a sparsely populated planet with low biodiversity. The two groups of animals that dominated the early Triassic were the...