There used to be the idea that dinosaurs were slow, stupid and unable to adapt to their environments – all of which led to their extinction. But this is not the case – for 150 million years dinosaurs, pterosaurs, ichthyosaurs and plesiosaurs ruled the land, the sea and the skies. Considering that humans have only been around approximately 4 million years, that is a pretty impressive record. I am not sure if we are going to make the 150 million year mark due to our arrogance and abuse of our planet, but that is another topic.
The dinosaurs lived in the geological Era called the Mesozoic which is subdivided into the Triassic, Jurassic and Cretaceous Periods. The era began in the wake of the Permian–Triassic extinction event, the largest mass extinction in Earth history, and ended with the Cretaceous–Paleogene (K-Pg) extinction event, the last great mass extinction which killed off the non-avian dinosaurs, plesiosaurs, pterasaurs and many other plant and animal species.
The Mesozoic lasted approximately 186 million years, from 252.17 to 66 million years ago when the Cainozoic Era began. The Mesozoic is divided into three geologic periods as follows:
- Triassic (252.17 to 201.3 million years ago)
- Jurassic (201.3 to 145 million years ago)
- Cretaceous (145 to 66 million years ago)
The Mesozoic world changed significantly from its beginnings at the start of the Triassic to the end at the End Cretaceous extinction event. Plate tectonics, popularly known as continental drift, caused continents to wander around the planet’s surface, taking them from polar regions to temperate and vice versa.
Here is a fantastic animation of Gondwana breakup http://www.reeves.nl/gondwana
Most notably the breakup of the supercontinent Pangaea occurred during this time. Climates changed not only due to continental drift but to changes in atmospheric chemistry, sea level changes, closing of sea ways due to plate tectonics, and Milankovich Cycles.
Vegetation at the beginning of the age of dinosaurs comprised low, shrubby, fern-lke plants, which evolved into vast coniferous forests and cycads. The big change was the evolution of flowering plants. Many of these plants are preserved in the fossil record and some of them are still living today – plants like cycads, magnolias, holly, ginkgo and conifers.
Non avian (avian = birds) dinosaurs first evolved in the late Triassic and became dominant by the early Jurassic, staying at the top of the pile for the next 135 million years, going extinct at the end of the Cretaceous. Birds first appeared in the Jurassic, and are considered to have evolved from a branch of theropod dinosaurs. Mammals only arrived late in the Mesozoic but remained small and insignificant until they got their chance after the dinosaurs went extinct.