02. Why did the dinosaurs die out?
DINOSAUR EXTINCTION THEORIES
The first dinosaur bones were probably discovered by Chinese scholars in antiquity. However, in Europe the first recorded discovery wasn’t until 1677. By 1842 it was realised that prehistoric reptiles had once inhabited the Earth. The name Dinosauria was proposed to describe this group.
Reptiles first appeared about 320 million years ago (Ma), towards the end of the Palaeozoic era. They flourished during the Mesozoic Era which is also referred to as the Age of Reptiles. This era is further subdivided into the following periods:
- Triassic (approx. 250 – 200Ma)
- Jurassic (approx. 200 – 145Ma)
- Cretaceous (approx. 145 – 65Ma)
Dinosaurs ruled the Earth for almost 150 million years. This spanned the Late Triassic, Jurassic and Cretaceous periods. One of the largest mass extinctions in Earth’s history occurred at the end of the Cretaceous period. It is referred to as the K-T (Cretaceous-Tertiary) extinction.
(K is the traditional abbreviation for the Cretaceous period, and the word Cretaceous is derived from the Greek word for chalk, Creta. The K-T extinction event is now called the Cretaceous–Paleogene (or K–Pg) event by many researchers.)
Many species, including dinosaurs, pterosaurs, and large marine reptiles, disappeared virtually overnight. Today the only living descendents of the dinosaurs are the birds.
Many theories have been suggested for the extinction of the dinosaurs. Some of these have dealt with:
- toxic volcanic gases and dust
- asteroid impact
- food shortage
- climate change
Some scientists have suggested a combination of these factors.