While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, and some were able to shift between these stances. Evidence suggests that all dinosaurs were egg-laying and that nest-building was a trait shared by many dinosaurs, both avian and non-avian. Some were herbivorous, others carnivorous. Most research conducted since the 1970s, however, has indicated that dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction.
Through the first half of the 20th century, before birds were recognized as dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded. Dinosaurs are represented on every continent by both extant species (birds) and fossil remains. Using fossil evidence, paleontologists have identified over 900 distinct genera and more than 1,000 different species of non-avian dinosaurs. Birds, at over 10,700 living species, are among the most diverse group of vertebrates. Dinosaurs can therefore be divided into avian dinosaurs, or birds and the extinct non-avian dinosaurs, which are all dinosaurs other than birds.ĭinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. The fossil record shows that birds are modern feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event approximately 66 million years ago. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 million years ago their dominance continued throughout the Jurassic and Cretaceous periods. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. Birds are avian dinosaurs, and in phylogenetic taxonomy are included in the group Dinosauria.ĭinosaurs are a diverse group of reptiles of the clade Dinosauria.
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