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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.
The shared history of birds and dinosaurs is well-established, but exactly how true birds evolved during the Mesozoic is a bit of a mystery. Adding to this conundrum are fossilized footprints of ...
In the 1970s, John Ostrom, following Thomas Henry Huxley's lead in 1868, argued that birds evolved within theropod dinosaurs and Archaeopteryx was a critical piece of evidence for this argument; it had several avian features, such as a wishbone, flight feathers, wings, and a partially reversed first toe along with dinosaur and theropod features.
The fossil filled a 70-million-year gap in the understanding of how the brains of birds evolved: between the 150-million-year-old Archaeopteryx, the earliest known bird-like dinosaur, and birds ...
Many more transitional fossils have been discovered since then, and there is now abundant evidence of how all classes of vertebrates are related, including many transitional fossils. [5] Specific examples of class-level transitions are: tetrapods and fish, birds and dinosaurs, and mammals and "mammal-like reptiles".
A remarkable event in dinosaur evolution came when small feathered two-legged dinosaurs from a lineage known as theropods gave rise to birds late in the Jurassic, with the oldest-known bird ...
Because Caudipteryx has clear and unambiguously pennaceous feathers, like modern birds, and because several cladistic analyses have consistently recovered it as a non-avian oviraptorid dinosaur, it provided, at the time of its description, the clearest and most succinct evidence that birds evolved from dinosaurs.