Evolution of the Dinosaurs

Dinosaurs First Appear

What are some of the earliest known primitive dinosaurs?

Two of the earliest known primitive dinosaurs were both fast-running carnivores: the Eoraptor, or “dawn hunter,” a small, three-foot-(one-meter-) long dinosaur that weighed about 22 pounds (10 kilograms); and the Herrerasaurus, measuring from 9 to 18 feet (3 to 6 meters) long. Both lived approximately 230 million years ago in the area known today as Argentina. Still another earlier dinosaur was the Staurikosaurus, a Late Triassic (around 225 million years ago) carnivore found in Brazil. It was about 6.5 feet (2 meters) long, with a fully upright gait that allowed for speed. After the evolution of these early specimens, other dinosaurs evolved quickly, becoming more and more diverse, and reachng out into all ecological niches.


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