Many different dinosaurs lived at other times during the Mesozoic era:
- Some dinosaurs walked on two legs, and some walked on four legs. Some could do both.
- Dinosaurs could not fly. However, other prehistoric reptiles could fly.
- Some dinosaurs could wade or paddle through the water. However, dinosaurs did not live in oceans, lakes, or rivers. Other prehistoric reptiles could swim and eat sharks.
- Some dinosaurs were fast and agile, while others were slow and lumbering.
- Some dinosaurs had thick and bumpy skin.
- Some dinosaurs had feathers.
- Some dinosaurs were armor-plated. Others had horns, spikes, or crests to defend themselves.
Dinosaurs can be grouped into the following categories:
Armored dinosaurs – these medium-sized, four-legged herbivores had body armor, and some even had tail spikes. Examples of armored dinosaurs include Gastonia, Stegosaurus, and Nodosaurus.
Ceratopsians – these dinosaurs were herbivores with parrot-like beaks, bony frills, and, sometimes, horns. Examples of ceratopsians include Triceratops, Centrosaurus, and Achelousaurus.
Euornithopods – these medium-sized herbivores usually walk on two legs. Examples of ornithopods include Iguanodon, Parasaurolophus, and Edmontosaurus.
Sauropods – these very large herbivores mostly walked on four legs. Examples of sauropods include Brachiosaurus, Diplodocus, and Pelorosaurus.
Large theropods – these large carnivores walked on two legs. Examples of large theropods include Carnotaurus, Allosaurus, and Tyrannosaurus rex.
Small theropods – these small carnivores, herbivores, and omnivores walked on two legs and sometimes had feathers. Examples of small theropods include Oviraptor, Troodon, and Velociraptor.