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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"]), commonly known as theropods, is an extant dinosaur clade that is ...
In theropod dinosaurs (carnivores that walked on two legs and had birdlike feet) flexible soft tissue air sacs likely pumped air through the stiff lungs, as is the case in birds. "What was once formally considered unique to birds was present in some form in the ancestors of birds", O'Connor said.
As scientists have discovered more theropods closely related to birds, the previously clear distinction between non-birds and birds has become blurred. By the 2000s, discoveries in the Liaoning Province of northeast China, which demonstrated many small theropod feathered dinosaurs , contributed to this ambiguity.
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.
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).
This list of non-avian theropod type specimens is a list of fossils that are the official standard-bearers for inclusion in the Mesozoic species and genera of the dinosaur clade Theropoda, which includes the carnivorous dinosaurs like Tyrannosaurus and Velociraptor, their herbivorous relatives like the therizinosaurs, and birds.
Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, and coelurosaurs (which includes tyrannosauroids, ornithomimosaurs, compsognathids and maniraptorans, the latter including living birds). [1]
In birds, some temperature control occurs in the respiratory system. [16] Water vapor heats cool air during inhalation in the trachea, and increases its humidity. [16] The resulting evaporative water loss varies greatly and depends on several factors including air sac pressure and the subsequent rate of air flow through the trachea.