Dinosaurs

Dinosaurs dominated the land for more than 140 million years (more than 160 million years in some regions). The diverse forms and sizes of dinosaurs, from the fearsome giant Spinosaurus to the chicken-sized Microraptor, allowed them to thrive in a variety of ecosystems.

Dinosaurs were successful because their back legs were straight, perpendicular to their bodies. As a result, they were able to use less energy to move than other reptiles that had a sprawling stance, such as today’s crocodiles and lizards.

Dinosaurs’ legs were positioned under their bodies rather than sticking out to the side, so their weight was also better supported. Figure showing the difference between an upright stance and a sprawling stance.

Crocodiles and lizards have a sprawling stance, while dinosaurs were upright. Around 66 million years ago, many dinosaur species went extinct, but there is still a group of living dinosaurs: birds.