Birds are avian dinosaurs, and phylogenetic taxonomy includes over 11,000 extant species in the group Dinosauria. Dinosaurs are a diverse group of reptiles [note 1] of the clade Dinosauria. 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. They …
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