Dinosaurs were the dominant land animals for 160 million years, making them one of the most successful groups of animals ever.The largest dinosaurs were over 100 feet long and up to 50 feet tall. The smallest dinosaurs were about the size of a chicken.
Dinosaurs lived during a period of Earth’s history called the Mesozoic ("middle life") Era. They lived during all three periods of this era: the Triassic, Jurassic, and Cretaceous.
The word dinosaur comes from the Greek language and means ‘terrible lizard’. The word was coined by English paleontologist Richard Owen in 1842 and was meant to refer to Dinosaurs impressive size rather than their scary appearance.
Most dinosaurs were plant-eaters (herbivores) about 65% of them.Meat-eating dinosaurs are known as theropods, which means "beast-footed," because they had sharp, hooked claws on their toes. In contrast, plant-eating dinosaurs tended to have blunt hooves or toenails.
No one really knows exactly how many dinosaur species exist. The estimates vary from between 250 to over 1300 species.
Dinosaur skulls had large holes or "windows" that made their skulls lighter. Some of the largest skulls were as long as a car.
Dinosaurs are divided into two groups by the structure of their hipbones. In the hips of saurischian, or lizard hipped, dinosaurs, one of the bones pointed forward. In the hips of ornithischian, or bird-hipped, dinosaurs, all the bones pointed backward. Ironically, scientists believe that birds evolved from lizard-hipped dinosaurs, not bird-hipped dinosaurs.
Pterodactyls are not dinosaurs, they were flying reptiles that lived during the age of dinosaurs but by definition they do not fall into the same category. The same goes for water based reptiles such as Plesiosaurs.
The largest dinosaur eggs were as large as basketballs. The bigger the egg, the thicker the shell. So if the eggs had been larger, dinosaur babies probably would not have been able to get out.