Ornithurae
Encyclopedia
Ornithurae is the name of a natural group which includes all modern bird
s as well as their extinct relatives with plough-shaped pygostyle
s, a bone at the end of the tail which allows the tail feathers to fan and retract.
coined the name in 1866 and included in the group all "true birds" with the "characteristic tail morphology of all extant birds" (translation by Jacques Gauthier
). This distinguishes the group from Archaeopteryx
, which Haeckel placed in another new group called Sauriurae
. Said simply, modern birds have short tails, while Archaeopteryx has a long tail like that of theropod dinosaur
s.
Gauthier converted Ornithurae into a clade
, giving it a branch-based definition: "extant birds and all other taxa, such as Ichthyornis
and Hesperornithes
, that are closer to extant birds than is Archaeopteryx
". Later he and de Queiroz redefined it as an apomorphy-based clade more in keeping with Haeckel's original usage, including the first panavian with a "bird tail" homologous with that of Vultur gryphus, and all of its descendants. They defined "bird tail" as a tail that is shorter than the femur, with a pygostyle
that is a ploughshare-shaped, compressed element, with the bones fused in the adult, composed of less than six caudal vertebrae, and shorter than the free part of the tail, which itself is composed of less than eight caudal vertebrae. They included Aves (which they defined as the "crown group
" of modern birds), Ichthyornis, Hesperornithes, and Apsaravis
in Ornithurae.
Neornithes was originally proposed as a replacement for Ornithurae by Gadow
in 1892 and 1893. Gauthier and de Queiroz, therefore, consider Neornithes a junior synonym of Ornithurae, though many other scientists use Neornithes to refer to the much more restrictive crown group consisting only of modern birds (a group for which Gauthier uses the name Aves). Alternately, some researchers have used Ornithurae to refer to a more restrictive node-based clade, anchored on Hesperornis
and modern birds.
Clarke at al. (2006) found that Yixianornis
, Songlingornis
, and Yanornis
form an unnamed clade which is the most basal group in the Ornithurae (following the apomorphy-based definition). They found that this group has a mosaic of advanced and primitive features. These three taxa retain primitive features like gastralia and a pubic symphysis
. They also show the first fully modern pygostyle
s, and the type specimen of Yixianornis (IVPP 13631) preserves eight elongated rectrices in a modern arrangement. No earlierpygostylia
ns are known which preserve a fan of rectrices of this sort; instead they show only paired plumes or a tuft of short feathers.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s as well as their extinct relatives with plough-shaped pygostyle
Pygostyle
Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these....
s, a bone at the end of the tail which allows the tail feathers to fan and retract.
Taxonomy
Ernst HaeckelErnst Haeckel
The "European War" became known as "The Great War", and it was not until 1920, in the book "The First World War 1914-1918" by Charles à Court Repington, that the term "First World War" was used as the official name for the conflict.-Research:...
coined the name in 1866 and included in the group all "true birds" with the "characteristic tail morphology of all extant birds" (translation by Jacques Gauthier
Jacques Gauthier
Jacques Armand Gauthier is a vertebrate paleontologist, comparative morphologist, and systematist, and one of the founders of the use of cladistics in biology....
). This distinguishes the group from Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
, which Haeckel placed in another new group called Sauriurae
Sauriurae
Sauriurae is a now-deprecated subclass of birds created by Ernst Haeckel in 1866. It was intended to include Archaeopteryx and distinguish it from all other birds then known, which he grouped in the sister-group Ornithurae...
. Said simply, modern birds have short tails, while Archaeopteryx has a long tail like that of theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s.
Gauthier converted Ornithurae into a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
, giving it a branch-based definition: "extant birds and all other taxa, such as Ichthyornis
Ichthyornis
Ichthyornis is a genus of toothed seabirds from the Late Cretaceous of North America. Its fossil remains are known from the chalks of Alberta, Alabama, Kansas, New Mexico, Saskatchewan, and Texas, in strata that were laid down in the Western Interior Seaway during the Turonian-Campanian ages,...
and Hesperornithes
Hesperornithes
Hesperornithes is an extinct and highly specialized clade of Cretaceous toothed birds. Hesperornithine birds, apparently limited to former aquatic habitats in the Northern Hemisphere, include genera such as Hesperornis, Parahesperornis, Baptornis, Enaliornis, and probably Potamornis, all...
, that are closer to extant birds than is Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
". Later he and de Queiroz redefined it as an apomorphy-based clade more in keeping with Haeckel's original usage, including the first panavian with a "bird tail" homologous with that of Vultur gryphus, and all of its descendants. They defined "bird tail" as a tail that is shorter than the femur, with a pygostyle
Pygostyle
Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these....
that is a ploughshare-shaped, compressed element, with the bones fused in the adult, composed of less than six caudal vertebrae, and shorter than the free part of the tail, which itself is composed of less than eight caudal vertebrae. They included Aves (which they defined as the "crown group
Crown group
A crown group is a group consisting of living representatives, their ancestors back to the most recent common ancestor of that group, and all of that ancestor's descendants. The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms...
" of modern birds), Ichthyornis, Hesperornithes, and Apsaravis
Apsaravis
Apsaravis is a Mesozoic bird genus from the Late Cretaceous. The single known species, Apsaravis ukhaana, lived about 78 million years ago, in the Campanian age of the Cretaceous period. Its fossilized remains were found in the Camel's Humps sublocality of the Djadokhta Formation, at Ukhaa...
in Ornithurae.
Neornithes was originally proposed as a replacement for Ornithurae by Gadow
Hans Friedrich Gadow
Hans Friedrich Gadow was a German ornithologist.Gadow was born in Pomerania, the son of an inspector of the Prussian royal forests. He studied at the universities of Berlin, Jena and Heidelberg. At Jena he studied under Ernst Haeckel and at Heidelberg under the anatomist Karl Gegenbaur...
in 1892 and 1893. Gauthier and de Queiroz, therefore, consider Neornithes a junior synonym of Ornithurae, though many other scientists use Neornithes to refer to the much more restrictive crown group consisting only of modern birds (a group for which Gauthier uses the name Aves). Alternately, some researchers have used Ornithurae to refer to a more restrictive node-based clade, anchored on Hesperornis
Hesperornis
Hesperornis is a genus of flightless aquatic birds that spanned the first half of the Campanian age of the Late Cretaceous period . One of the lesser-known discoveries of the paleontologist O. C. Marsh in the late 19th century Bone Wars, it was an important early find in the history of avian...
and modern birds.
Clarke at al. (2006) found that Yixianornis
Yixianornis
Yixianornis is a bird genus from the early Cretaceous period. Its remains have been found in the Jiufotang Formation at Chaoyang dated to the early Aptian age, around 120 million years ago. Only one species, Yixianornis grabaui, is known at present...
, Songlingornis
Songlingornis
Songlingornis is a prehistoric bird genus from the Early Cretaceous. Its fossils have been found in the Jiufotang Formation of Liaoning . The age of these rocks is somewhat disputed, but probably around the early Aptian, 125-120 million years ago...
, and Yanornis
Yanornis
Yanornis is an extinct genus of omnivorous Early Cretaceous birds, thought to be closely related to the common ancestor of all modern birds. One species, Yanornis martini,...
form an unnamed clade which is the most basal group in the Ornithurae (following the apomorphy-based definition). They found that this group has a mosaic of advanced and primitive features. These three taxa retain primitive features like gastralia and a pubic symphysis
Pubic symphysis
The pubic symphysis or symphysis pubis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis...
. They also show the first fully modern pygostyle
Pygostyle
Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these....
s, and the type specimen of Yixianornis (IVPP 13631) preserves eight elongated rectrices in a modern arrangement. No earlierpygostylia
Pygostylia
Pygostylia is a group of birds which includes Confuciusornis and all of the more derived birds; the Ornithothoraces. Chiappe defined the Pygostylia as "the common ancestor of the Confuciusornithidae and Neornithes plus all its descendants". This is a node-based definition.Chiappe united the...
ns are known which preserve a fan of rectrices of this sort; instead they show only paired plumes or a tuft of short feathers.