Ornithurae (meaning "bird tails" in Greek) is a natural group which includes the common ancestor of Ichthyornis, Hesperornis, and all modern birds as well as all other descendants of that common ancestor.
|Cast skeleton of Ichthyornis dispar, Rocky Mountain Dinosaur Resource Center|
|Australian brushturkey (Alectura lathami)|
Ernst Haeckel 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, fused pygostyle tails, while Archaeopteryx retained the long tail characteristic of non-avian theropod dinosaurs.
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 pan-avian 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.
The cladogram below is the result of a 2014 analysis by Michael Lee and colleagues that expanded on data from an earlier study by O’Connor & Zhou in 2012. The clade names are positioned based on their definitions.
Ambiortiformes is a group of prehistoric birds.
The first species to be included, Ambiortus dementjevi, lived sometime during the Barremian age between 136.4 and 125 million years ago in today's Mongolia. A. dementjevi belongs to the Ornithuromorpha (the group containing modern birds but not enantiornithes), according to all published cladistic analyses. However, the exact position of the species within this group has been controversial. Most analyses have found it to be either an unresolved member of the Ornithurae, or a more primitive member of Ornithuromorpha. One 2006 study, for example, found it to be more primitive than Yanornis but more advanced than Hongshanornis, or even a member of the specific group containing both Yanornis and Yixianornis.The group includes at least Ambiortus and possibly the supposed close relative Apsaravis. The results of a cladistic analysis published in 2011 indicate that Apsaravis and Palintropus are very closely related.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 Tolgod in the Gobi Desert of Mongolia. They were collected in the 1998 field season by the Mongolian Academy of Sciences/American Museum of Natural History Paleontological Expeditions. It was described by Norell and Clarke (2001).Its habitat was presumably very arid open landscape much like it is today, perhaps hotter still and with more (but nonetheless intermittent) rain. Permanent freshwater would have been scarce.Archaeorhynchus
For the prehistoric weevil genus, see Archaeorrhynchus.
Archaeorhynchus is a genus of beaked avialans (proto-birds) from the early Cretaceous period. A fossil of its only known species, Archaeorhynchus spathula, was first reported in 2005 by Zhou & Zhang to have been found in Yixian Formation rocks at Yixian, Liaoning province, China, showing a well-preserved and essentially complete skeleton. Two more complete specimens were found in Lower Cretaceous deposits of Jianchang, Liaoning, northeastern China, preserving new anatomical information. These deposits are 120 million years old, whereas the original specimen was 125 million years old, meaning the age range for this species is 125-120Ma.Archaeorhychus is one of the earliest avialans known to have had a beak, and represents one of the most basal ornithuromorph avialans. The fossils preserved feathers associated with the neck, head and tail regions. The fossils also show grooves and openings/ holes (foramina) on the tips of the upper and lower jaws, suggesting that it supported a horny bill. Other features present suggest powerful flight capability similar to that of some modern birds. It has also been suggested that it had an herbivorous diet based on preserved gizzard stones found in its stomach.Changzuiornis
Changzuiornis is an extinct genus of ornithuromorph bird from the Early Cretaceous of present-day China. It contains a single species, C. ahgmi.Chaoyangia
Chaoyangia is an extinct genus of euornithean birds, containing the single species Chaoyangia beishanensis. This species is known from a single fossil specimen consisting of a partial skeleton including vertebra, ribs, hips, and upper legs. The specimen (museum catalog number IVPP V9934) was discovered in the Jiufotang Formation near the city of Chaoyang in Liaoning province, China. This rock formation has been dated to the Aptian age of the Early Cretaceous period, 120 million years ago.Dingavis
Dingavis is an extinct genus of ornithuromorph bird from the Early Cretaceous of present-day China. It contains a single species, D. longimaxilla.Euornithes
Euornithes (from Greek ευόρνιθες euórnithes meaning "true birds") is a natural group which includes the most recent common ancestor of all avialans closer to modern birds than to Sinornis.Gallornis
Gallornis is a genus of prehistoric birds from the Cretaceous. The single known species Gallornis straeleni lived near today's Auxerre in Yonne département (France); it has been dated very tentatively to the Berriasian-Hauterivian stages, that is about 140–130 million years ago. The known fossil material consists of a worn partial femur and a fragment of the humerus.This is a highly significant taxon for theories about the evolution of birds. Unfortunately, it is not known from much or well-preserved material. It has been proposed that the remains show features only known from the Neornithes – the group of birds that exists today. Thus, the Gallornis fossils suggest that as early as about 130 million years ago or more the ancestors of all living birds might already have been an evolutionary lineage distinct from the closely related Hesperornithes and Ichthyornithes (essentially modern birds retaining some more ancient features like teeth) and the more distantly related Enantiornithes (a group of more primitive toothed birds which were the most successful avians in the Mesozoic).Gansus
Gansus is a genus of aquatic birds that lived during the Aptian age of the Early Cretaceous (Aptian-Albian) period in what are now Gansu and Liaoning provinces, western China. The rock layers from which their fossils have been recovered are dated to 120 million years ago. It was first described in 1984 on the basis of an isolated left leg. It is the oldest-known member of the Ornithurae, the group which includes modern birds (Neornithes) and extinct related groups, such as Ichthyornis and Hesperornithes.Gargantuavis
Gargantuavis is a genus of extinct Ornithurine stem-birds containing the single species Gargantuavis philoinos. It is the only member of the monotypic family Gargantuaviidae. G. philoinos lived during the late Cretaceous period in what is now southern France and northern Spain. Its fossils were discovered in several formations, which has been dated between 73.5 and 71.5 million years old. Gargantuavis is the largest known bird of the Mesozoic. The few known bones suggests a size between the cassowary and the ostrich. A study based on the circumference of the femur gives a mass of 140 kg (310 lb) like modern ostriches. Given its mass Gargantuavis was probably flightless. Its femur shows that it was a graviportal form rather than a cursorial bird. Many aspects of its biology are unknown including its diet (the skull has not yet been found). The ecological niche of Gargantuavis in its ecosystem is also mysterious because it coexisted with large predators like abelisaurids theropods. In any case, and contrary to older assumptions, Gargantuavis shows that the extinction of non-avian dinosaurs was not a necessary condition for the emergence of giant terrestrial birds. It is possible that some of the fossil eggs found in the region, usually attributed to non-avialan dinosaurs, actually belong to this bird.Hollanda luceria
Hollanda is a genus of small ground birds known from fossils found in the Barun Goyot Formation of Mongolia. Found at Khermeen Tsav, it dates from the late Cretaceous period (Campanian stage), about 75 million years ago. Known only from partial hind limbs, Hollanda has long legs with an unusual configuration of the toes. These indicate that it was a fast-running ground bird, possibly similar to the modern Roadrunner. Its relationships are uncertain. Some studies have found that it was an relatively advanced bird, a member of the Ornithurae, related to birds like Ichthyornis. Other studies have recovered it as a member of the primitive family Songlingornithidae.Hongshanornis
Hongshanornis is a genus of ornithuromorph birds known from early Cretaceous lake deposits of the Yixian Formation, Inner Mongolia, China. The holotype specimen, recovered in 2005, is currently held by the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. It was found in the Jianshangou fossil beds, dated to 124.6 million years ago. Three additional specimens have been reported, though only one of those has been definitively identified as belonging to Hongshanornis. This latter specimen was found in the Dawangzhangzi fossil beds, which are about 122 million years old.Hongshanornis is a member of the group Hongshanornithidae, to which it lent its name. It is closely related to Longicrusavis, which existed alongside Hongshanornis in the Dawangzhangzi ecosystem, and is very similar to the later Parahongshanornis from the Jiufotang Formation.Ichthyornithes
Ichthyornithes is an extinct group of toothed avialans very closely related to the common ancestor of all modern birds. They are known from fossil remains found throughout the late Cretaceous period of North America, though only one species, Ichthyornis dispar, is represented by complete enough fossils to have been named. Ichthyornitheans became extinct at the Cretaceous–Paleogene boundary, along with enantiornitheans, all other non-avian dinosaurs, and many other animal and plant groups.Jianchangornis
Jianchangornis a genus of basal ornithuromorph birds. Fossils were recovered from the Jiufotang Formation at Liaoning, People's Republic of China.Juehuaornis
Juehuaornis is an extinct genus of ornithuromorph bird from the Early Cretaceous of present-day China. It contains a single species, J. zhangi.Liaoningornis
Liaoningornis (meaning "bird of Liaoning" in Greek) is a genus of bird from Lower Cretaceous China. It was collected from the dinosaur-bearing beds of the Sihetun locality, of the Yixian Formation, Shangyuan, near the city of Beipiao in Liaoning province. The only known species is Liaoningornis longidigitris. It was described by Linhai Hou in 1996 and 1997.The single fossil is an incomplete semi-articulated skeleton the size of a sparrow. It includes both feet, the right leg, the sternum, part of the right arm, and fragmentary coracoids and pubes. Its accession number is IVPP11303. It is in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. It has advanced flight, perching, and respiratory adaptations like a long, deeply keeled sternum, a pair of anterolateral processes on the sternum near the articulations with the coracoids, fused, short, metatarsals, and highly curved pedal claws indicating good perching ability. Hou et al. (1996) described the metatarsals as fused only distally, but Zhou and Hou (2002) revised this analysis, finding that the metatarsus was fused distally and proximally, but not along most of the length.Zhou and Hou in 2002 considered Liaoningornis to be the oldest known member of the Ornithurae. However, a 2012 re-analysis by Jingmai O'Connor showed that it was in fact an enantiornithine similar to Eoalulavis.Pengornis
Pengornis is the largest known enantiornithine bird from the Early Cretaceous of northeast China. The name derives from "Peng", which refers to a mythological bird from Chinese folklore, and "-ornis", which means bird in Greek.
Pengornis is known from a single adult fossil, described by Zhou et al. in 2008. This holotype is in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing China. Its accession number is IVPP V15336. It was collected from the Jiufotang Formation, at Dapingfang, Chaoyang, Liaoning China. A second, juvenile specimen was described by Hu, Zhou, and O'Connor in 2014.
Pengornis shows characters of the humeral head, acromion, and anterior cervical vertebrae, that were previously known only in members of the Ornithurae. A phylogenetic analysis by Zhou et al. reduces to just three the number of characters that support enantiornithine monophyly. Thus, Pengornis supports the possibility that enantiornithines and Ornithurines may not be distinct clades.(see Apsaravis)Tingmiatornis
Tingmiatornis (meaning "bird that flies") is a genus of flighted and possibly diving ornithurine bird from the High Arctic of Canada. The genus contains a single species, T. arctica, described in 2016, which lived during the Turonian epoch of the Cretaceous.Zhyraornis
Zhyraornis is a genus of prehistoric bird from the late Cretaceous period (middle Turonian, 92 mya). Its fossils have been found in Bissekty Formation deposits near Dzharakuduk in the Kyzyl Kum, Uzbekistan. Two species have been assigned to this genus: Zhyraornis kashkarovi and Zhyraornis logunovi. Both are known only from partial pelvic bones (synsacra).