16-437: Ornithothoraces is a group of avialan dinosaurs that includes all enantiornithes ("opposite birds") and the euornithes ("true birds"), which includes modern birds and their closest ancestors. The name Ornithothoraces means "bird thoraxes". This refers to the modern, highly advanced anatomy of the thorax that gave the ornithothoracines superior flight capability compared with more primitive avialans. This anatomy includes
32-855: A better sense of smell. The following cladogram is based on the analysis by Hartman et al . (2019), which found flight likely evolved five separate times among paravian dinosaurs, two of those among Avialae (in Scansoriopterygids and other avialans). Archaeopteryx and "anchiornithids" were placed in Deinonychosauria, Avialae's sister group. † Archaeopterygidae † Unenlagiidae † Dromaeosauridae † Troodontidae † Scansoriopterygidae † Yandangornis † Bauxitornis † Balaur † Shenzhouraptor † Jixiangornis † Zhongornis † Sapeornis † Confuciusornithidae † Changchengornis † Chongmingia † Jinguofortis † Zhongjianornis Ornithothoraces In
48-426: A definition similar to "all theropods closer to birds than to Deinonychus ." A nearly identical definition, "the theropod group that includes all taxa closer to Passer than to Dromaeosaurus ", was used by Agnolín and Novas (2013) for their clade Averaptora , operating under the assumption that troodontids and birds were more closely related to each other than to dromaeosaurs. They also redefine Avialae as
64-407: A large, keeled breastbone, elongated coracoids and a modified glenoid joint in the shoulder, and a semi-rigid rib cage. In spite of this at least the sternum seems to have developed convergently rather than being a true homology . The earliest known members of the group are the enantiornitheans Protopteryx fengningensis , Eopengornis martini , and Cruralispennia multidonta , as well as
80-892: A node-based clade , the common ancestor of Iberomesornis romerali and modern birds, and all of its other descendants. In 1998, Paul Sereno defined Ornithothoraces in the same way, but used Sinornis santensis instead of Iberomesornis romerali . The cladogram below follows the results of a phylogenetic analysis by Wang et al. , 2016: † Protopteryx † Pengornithidae † Eoenantiornis † Bohaiornithidae † Fortunguavis † Longipterygidae † Eocathayornis † Cathayornis † Vescornis † Neuquenornis † Gobipteryx † Eoalulavis † Qiliania † Concornis † Archaeorhynchus † Patagopteryx † Vorona † Schizooura † Hongshanornithidae † Jianchangornis † Songlingornithidae † Gansus † Apsaravis Ornithurae [REDACTED] [REDACTED] Avialan Avialae ("bird wings")
96-399: 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). Archaeopteryx lithographica , from the late Jurassic Period Solnhofen Formation of Germany , is usually considered
112-410: Is also occasionally defined as an apomorphy-based clade (that is, one based on derived characteristics that were not present among lineage predecessors). Jacques Gauthier , who named Avialae in 1986, re-defined it in 2001 as all dinosaurs that possessed feathered wings used in flapping flight , and the birds that descended from them. The clade Avialae was given a formal phylogenetic definition in
128-464: The PhyloCode by Juan Benito and colleagues in 2022 as "the largest clade containing Vultur gryphus , but not Dromaeosaurus albertensis and Saurornithoides mongoliensis ". This definition ensures that both dromaeosaurids and troodontids are excluded from Avialae . Gauthier and de Queiroz (page 34) identified four conflicting ways of defining the term "Aves", which is a problem since
144-726: The Tiaojishan Formation of China , which has been dated to the late Jurassic period ( Oxfordian stage), about 160 million years ago. The avialan species from this time period include Anchiornis huxleyi and Aurornis xui . Xiaotingia zhengi used to be considered a member, but was later classified within the clade Dromaeosauridae . The well-known Archaeopteryx dates from slightly later Jurassic rocks (about 155 million years old) from Germany . Many of these early avialans shared unusual anatomical features that may be ancestral to modern birds, but were later lost during bird evolution. These features include enlarged claws on
160-441: The earliest known avialan which may have had the capability of powered flight; a minority of studies have suggested that it might have been a deinonychosaur instead. Several older (but non flight-capable) possible avialans are known from the late Jurassic Tiaojishan Formation of China , dated to about 160 million years ago. Most researchers define Avialae as branch-based clade, though definitions vary. Many authors have used
176-616: The euornithine Archaeornithura meemannae , all from the Sichakou Member of the Huajiying Formation in China , which has been dated to 130.7 million years old. At least one other enantiornithean, Noguerornis gonzalezi , may be even older, at up to 145.5 million years ago, though its exact age is uncertain. In 1994, Chiappe and Calvo established a phylogenetic definition of the group. They defend Ornithothoraces as
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#1732791024524192-534: The field of paleontology and bird evolution, though the exact definitions applied have been inconsistent. Avialae, initially proposed to replace the traditional fossil content of Aves, is sometimes used synonymously with the vernacular term "bird" by these researchers. † Anchiornis † Archaeopteryx † Rahonavis † Jixiangornis † Jeholornis [REDACTED] † Sapeornis † Confuciusornis [REDACTED] † Chongmingia Ornithothoraces [REDACTED] The earliest known avialans come from
208-437: The latter were lost independently in a number of avialan groups, including modern birds (Aves). While the earliest forms, such as Archaeopteryx and Shenzhouraptor , retained the long bony tails of their ancestors, the tails of more advanced avialans were shortened with the advent of the pygostyle bone in the group Pygostylia . In the late Cretaceous, around 95 million years ago, the ancestor of all modern birds also evolved
224-471: The same biological name is being used four different ways. They proposed a solution, number 4 below, which is to reserve the term Aves only for the crown group , the last common ancestor of all living birds and all of its descendants. Other definitions of Aves found in literature were reassigned to other clade names. Under the fourth definition Archaeopteryx is an avialan, and not a member of Aves. Gauthier's proposals have been adopted by many researchers in
240-542: The second toe which may have been held clear of the ground in life, and long feathers or "hind wings" covering the hind limbs and feet, which may have been used in aerial maneuvering. It is also thought that early avialans were either cranially akinetic or had otherwise limited cranial kinesis . Avialans diversified into a wide variety of forms during the Cretaceous Period . Many groups retained primitive characteristics , such as clawed wings and teeth, though
256-552: The smallest clade containing Archaeopteryx and modern birds. Additionally, beginning in the late 2000s and early 2010s, several groups of researchers began adding the genus Troodon as an additional specifier in the definition of Avialae. Troodon had long been considered a close relative of the dromaeosaurids in the larger group Deinonychosauria, though some contemporary studies found it and other troodontids more closely related to modern birds, and so it has been specifically excluded from Avialae in more recent studies. Avialae
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