History of dinosaur NOSAUR
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For other uses, see Dinosaur (disambiguation)
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. 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. 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. 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. Dinosaurs can therefore be divided into avian dinosaurs, or birds; and the
extinct non-avian dinosaurs, which are all dinosaurs other than birds.
Birds, at over 10,700 living species, are among the most diverse group of vertebrates.
Using fossil evidence, paleontologists have identified over 900 distinct genera and
more than 1,000 different species of non-avian dinosaurs. Dinosaurs are represented
on every continent by both extant species (birds) and fossil remains. 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.
Most research conducted since the 1970s, however, has indicated that dinosaurs
were active animals with elevated metabolisms and numerous adaptations for social
interaction. Some were herbivorous, others carnivorous. Evidence suggests that all
dinosaurs were egg-laying; and that nest-building was a trait shared by many
dinosaurs, both avian and non-avian
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