Any of the extinct reptiles that were the dominant land animals during most of the Mesozoic Era (251 – 65 million years ago). The various species appeared at different times, and not all overlapped. The shape of the teeth reveal whether a given dinosaur was a carnivore or an herbivore. Dinosaurs are classified as either ornithischians or saurischians, based on pelvic girdle structure. Most had a long tail, which they held straight out, apparently to maintain balance. Most, if not all, were egg layers. Some were probably warm-blooded. Dinosaur fossils have been found on every continent, including Antarctica. Most types of dinosaurs flourished until late in the Cretaceous Period (65 million years ago), then disappeared within the next million years. Two theories for the cause of this mass extinction following some 140 million years of existence are that volcanism and mountain-building cycles altered the habitat and changed the climate or that an asteroid hit Earth, resulting in immense dust clouds that blocked sunlight for several years. Birds and crocodiles are thought to be living descendants of the dinosaurs.
Dinosaur era
Dinosaur era Cretaceous
Tyrannosaurus
Brachiosaurus
Pterosaur
Mosasaurus
Stygimoloch
Stygimoloch
Styracoaurus
Elasmosaurus
Gallimimus
Gallimimus
Dinosaur era Jurassic
stegosaurus
Dinosaur era Triassic
Mussaurus
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