are the preserved remains or traces of animals, plants, and other organisms from the remote past.The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record.
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Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints.
Birds, at over 10,000 living species, Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded.
Clockwise from top left: Microraptor gui (a winged theropod), Apatosaurus louisae (a giant sauropod), Edmontosaurus regalis (a duck-billed ornithopod), Triceratops horridus (a horned ceratopsian), Stegosaurus stenops (a plated stegosaur), Pinacosaurus grangeri (an armored ankylosaur) Dinosaurs are a diverse group of reptiles of the clade Dinosauria that first appeared during the Triassic period.
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 million years ago.
Most research conducted since the 1970s, however, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction. Evidence suggests that egg laying and nest building are additional traits shared by all dinosaurs.
While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, and some were able to shift between these stances.Radiometric dating relies on the properties of isotopes.These are chemical elements, like carbon or uranium, that are identical except for one key feature -- the number of neutrons in their nucleus.If dinosaur fossils are at least 65 million years old, how has this biological material survived?How could these bones not yet be fully fossilized even after millions of years?Fossils may also consist of the marks left behind by the organism while it was alive, such as animal tracks or feces (coprolites).