# Dinosaur Information

## Introduction
Dinosaurs were a diverse group of reptiles that lived during the Mesozoic Era, which spanned from about 252 to 66 million years ago. They dominated Earth's ecosystems for over 160 million years until their mass extinction event at the end of the Cretaceous period.

## Classification
Dinosaurs are divided into two main groups:

1. **Saurischia** (Lizard-hipped dinosaurs)
   - Theropoda: Bipedal carnivores and some omnivores (e.g., T. rex, Velociraptor)
   - Sauropodomorpha: Herbivorous long-necked giants (e.g., Brachiosaurus, Apatosaurus)

2. **Ornithischia** (Bird-hipped dinosaurs)
   - Ornithopoda: Herbivorous bipedal dinosaurs (e.g., Iguanodon)
   - Ceratopsia: Horned herbivores (e.g., Triceratops)
   - Ankylosauria: Armored herbivores (e.g., Ankylosaurus)

## Notable Species
- **Tyrannosaurus rex**: One of the largest land carnivores, with a bite force strong enough to crush bone.
- **Velociraptor**: Small but intelligent pack hunters known for their sickle-shaped claw.
- **Brachiosaurus**: A massive sauropod with long front legs and neck adapted for browsing high vegetation.
- **Triceratops**: Famous for its three horns and large bony frill.

## Diet and Behavior
Dinosaurs had varied diets:
- Carnivores hunted other animals or scavenged.
- Herbivores fed on plants, requiring constant grazing due to short lifespans of food sources.

Many were likely social, living in packs or herds for protection and cooperative hunting.

## Extinction Event
Approximately 66 million years ago, a massive asteroid impact (Chicxulub crater) caused catastrophic climate changes, leading to the extinction of non-avian dinosaurs. Birds, however, are direct descendants of certain theropod lineages and survived.

## Legacy
Today, we celebrate dinosaurs not just as ancient creatures but as ancestors of modern birds, continuing their legacy in today's skies.