The Long Reign of Dinosaurs Before Extinction

Dinosaurs dominated Earth for an astonishing 165 million years, a period far longer than humans have existed. Their reign began in the Late Triassic period, approximately 230-235 million years ago, and concluded abruptly at the end of the Cretaceous period, about 66 million years ago, with the Cretaceous-Paleogene (K-Pg) extinction event.

This vast stretch of time is known as the Mesozoic Era, often called the "Age of Reptiles," and is divided into three distinct periods:

1. Triassic Period (approx. 252 to 201 million years ago): Dinosaurs first appeared during the Late Triassic, evolving from earlier archosaurs. They were initially smaller and coexisted with other large reptiles.
2. Jurassic Period (approx. 201 to 145 million years ago): This was the golden age for many iconic dinosaur groups, including the massive sauropods (like Brachiosaurus) and formidable theropods (like Allosaurus). Dinosaurs became the dominant terrestrial vertebrates across the globe.
3. Cretaceous Period (approx. 145 to 66 million years ago): Dinosaurs continued to thrive and diversify, with new forms like Tyrannosaurus Rex and Triceratops emerging. Flowering plants also evolved during this period, changing ecosystems significantly.

Their dominance ended with a catastrophic asteroid impact, leading to global environmental devastation and the extinction of all non-avian dinosaurs, along with about 75% of plant and animal species on Earth.

Pro tip: To put their 165-million-year reign into perspective, modern humans (Homo sapiens) have only been around for about 300,000 years. If Earth's history were a 24-hour clock, dinosaurs ruled for several hours, while human history is just a few seconds.