Dinosaurs were incredibly diverse, ranging from small, bird-like creatures to massive, towering giants, but how many different types were there?
When did dinosaurs first appear?
Dinosaurs roamed the Earth from approximately 245 to 66 million years ago, during the Mesozoic Era, which is often referred to as the "Age of Dinosaurs." This era is divided into three distinct periods: the Triassic, Jurassic, and Cretaceous.
The Triassic (252-201 million years ago) marked the emergence of the first dinosaurs (tentatively thought to be the Nyasasaurus according to the Natural History Museum), while the Jurassic (201-145 million years ago) saw the rise of large, herbivorous dinosaurs and the first birds. The Cretaceous (145-66 million years ago) was the final period, known for the dominance of famous dinosaurs like T. rex and Triceratops
How many species of dinosaurs were there?
So far about 1,000 non-avian dinosaurs have been identified in the fossil record, but a mathematical model estimates that around 2,000 species of dinosaur existed during the Mesozoic era – around 500 ornithischians, 500 sauropods and 1,000 of the more diverse theropods.
Confusingly, birds are not descended from the ‘bird-hipped’ ornithischian group, but from ‘reptile-hipped’ theropods, which means pterosaurs, the Jurassic Park star, are not dinosaurs