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Debates about the origin of bird flight are almost as old as the idea that birds evolved from dinosaurs, which arose soon after the discovery of Archaeopteryx in 1862. Two theories have dominated most of the discussion since then: the cursorial ("from the ground up") theory proposes that birds evolved from small, fast predators that ran on the ...
The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Paraves. [1] Birds are categorized as a biological class , Aves. For more than a century, the small theropod dinosaur Archaeopteryx lithographica from the Late Jurassic period was considered to have been the earliest bird.
Beginning of animal evolution. [54] [55] 720–630 Ma Possible global glaciation [56] [57] which increased the atmospheric oxygen and decreased carbon dioxide, and was either caused by land plant evolution [58] or resulted in it. [59] Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution. [60] [61] [62 ...
Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds, and their closest relatives.It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally used (see below).
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Dromaeosauridae, Troodontidae, Oviraptorosauria, and Therizinosauria. Ornitholestes and the Alvarezsauroidea are also often included.
The age of the dinosaurs never really ended—it only evolved. Birds (and their more reptilian cousins, the Crocodilia ) are the modern-day legacy of dinosaur’s 165-million-year-long stint on Earth.
Ornithischian (bird-hipped) dinosaurs had a pelvis shape similar to that of birds, or avian dinosaurs, which evolved from saurischian (lizard-hipped) dinosaurs. [71] The Heterodontosauridae evolved a tibiotarsus which is also found in modern birds. These groups are not closely related. [72] Ankylosaurs and glyptodont mammals both had spiked ...
An alternate name is Pan-Aves, or "all birds", in reference to its definition containing all animals, living or extinct, which are more closely related to birds than to crocodilians. [4] Although dinosaurs and pterosaurs were the only avemetatarsalians to survive past the end of the Triassic, other groups flourished during the Triassic.