Dinosaurs
Dinosaurs were a diverse group of reptiles of the clade Dinosauria. They first appeared during the Mesozoic Era, which is divided into three periods: the Triassic, Jurassic, and Cretaceous. Dinosaurs dominated the terrestrial ecosystems for over 160 million years. They were a highly successful group of animals, with an incredible range of sizes, shapes, and ecological adaptations.
Dinosaur Classification
Dinosaurs are classified into two main groups: the Saurischia and the Ornithischia. The Saurischia includes the theropods (such as Tyrannosaurus rex and Velociraptor) and the sauropodomorphs (such as Brachiosaurus and Diplodocus). The Ornithischia includes the herbivorous dinosaurs such as Stegosaurus and Triceratops.
Dinosaur Anatomy
Dinosaurs were vertebrates, meaning they had a backbone and a well-defined skull. They were also diapsids, meaning they had two holes in their skulls behind their eyes. Many dinosaurs were bipedal, walking on two legs, while others were quadrupedal, walking on four legs. They had a wide range of adaptations for feeding, locomotion, and defense.
Dinosaur Extinction
One of the most intriguing aspects of dinosaurs is their extinction. The prevailing theory is that a massive asteroid impact, combined with volcanic activity, led to global climate change and the eventual extinction of non-avian dinosaurs at the end of the Cretaceous period, approximately 66 million years ago.
Study Guide
- Describe the main characteristics of the two main groups of dinosaurs, the Saurischia and the Ornithischia.
- Explain the difference between theropod and sauropodomorph dinosaurs, providing examples of each.
- Discuss the possible reasons for the extinction of non-avian dinosaurs at the end of the Cretaceous period.
- Compare and contrast the anatomy of bipedal and quadrupedal dinosaurs, providing examples of each.
- Research and present a timeline of the Mesozoic Era, including the three periods and significant events that occurred during each period.
