Origins of Birds Actions Share Share Share to social media Facebook X URL https://www.britannica.com/animal/Origins-of-Birds Share Share Share to social media Facebook X URL https://www.britannica.com/animal/Origins-of-Birds Written and fact-checked by The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors. The Editors of Encyclopaedia Britannica Last Updated: Aug 14, 2024 • Article History Table of Contents According to nearly all ornithologists, birds are not only the descendants of ancient dinosaurs, they are, in fact, dinosaurs themselves! Dinosaurs are a branch of reptiles that emerged during the middle of the Triassic Period (about 252 million to 201 million years ago) and thrived during the Jurassic and Cretaceous periods (201 million to 66 million years ago). Birds evolved from a group of dinosaurs called theropods, which are known for the ability to walk on their hind legs rather than on all fours. The slow transformation of part of this lineage into the forms we recognize as birds was ...(100 of 402 words)

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