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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.
A turning point came in the early twentieth century with the writings of Gerhard Heilmann of Denmark.An artist by trade, Heilmann had a scholarly interest in birds and from 1913 to 1916, expanding on earlier work by Othenio Abel, [12] published the results of his research in several parts, dealing with the anatomy, embryology, behavior, paleontology, and evolution of birds. [13]
The evolution of birds is thought to have begun in the Jurassic Period, with the earliest birds derived from theropod dinosaurs. Birds are categorized as a biological class, Aves. The earliest known species in Aves is Archaeopteryx lithographica, from the Late Jurassic period. Modern phylogenetics place birds in the dinosaur clade Theropoda.
In the modern fauna, theropods are represented by over 11,000 species of birds, which are a group of maniraptoran theropods within the clade Avialae.. Theropoda (/ θ ɪəˈr ɒ p ə d ə /; [2] from ancient Greek θηρίο-ποδός [θηρίον, (therion) "wild beast"; πούς, ποδός (pous, podos) "foot"]), whose members are known as theropods, is an extant dinosaur clade that is ...
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. ... “Fossil tracks of early birds and theropods, the ...
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).
The earliest birds with a modern pygostyle: a reduction and fusion of the tail vertebrae; possibly a paraphyletic group. Two types of pygostyle are known, a rod-shaped one found in Confuciusornithidae, Enantiornithes and some non-avian theropods such as Nomingia, and a plowshare-shaped one
The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming. The study of birds is called ornithology. Birds are feathered theropod dinosaurs and constitute the only known living dinosaurs.