The Triassic-Jurassic Mass Extinction took place about 200 million years ago, just 50 million years after the "Great dying" event. There were 2 or 3 phases of extinction in this event and it happened just less than 10,000 years -- can be treated a blink of a geological eye.
In this event, more than half of all species died out on Earth. It killed about 20% of marine families and 30% of marine genera. Many of the "mammal-like raptiles", which are known as therapsids, became extinct in the mass extinction. Besides, all large cruotarsans (non-dinosaur archosaurs, the ancestors of modern-day crocodiles, alligators and gavials) and most large amphibians were also died out after that period of time[1].
At this boundary of time, dinosaurs were appeared on Earth[2], but only about 1-2% of fauna. As the mass extinction wiped out those life mentioned above, the living environment became better for dinosaurs as there were less food competition. After the event, the percentage of dinosaurs increased to 50-90% of fauna. Because of these reasons, the Triassic-Jurassic Mass Extinction is often treated as the event leading the stage for dinosaurs to dominant the world at that time.
Reference:
1. http://www.wisegeek.com/what-is-the-triassic-jurassic-extinction-event.htm
2. http://io9.com/Triassic-jurassic-extinction-event/
No comments:
Post a Comment