Elaborate display structures such as horns or crests are common to all dinosaur groups, and some extinct groups developed skeletal modifications such as bony armor and spines. 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 groups of vertebrates. Dinosaurs can therefore be divided into avian dinosaurs-birds-and the extinct non-avian dinosaurs, which are all dinosaurs other than birds.ĭinosaurs are varied from taxonomic, morphological and ecological standpoints. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya.
They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout the Jurassic and Cretaceous periods. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is a subject of active research. † Silesauridae? ( paraphyletic?) īirds 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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