Aurornis Temporal range: Late Jurassic, | |
---|---|
Life restoration | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | † Anchiornithidae |
Genus: | † Aurornis Godefroit et al., 2013 |
Type species | |
†Aurornis xui Godefroit et al., 2013 |
Aurornis is an extinct genus of anchiornithid theropod dinosaurs from the Jurassic period of China. The genus Aurornis contains a single known species, Aurornis xui ( /aʊˈrɔːrnɪsˈʃuːi/ ). [1] Aurornis xui may be the most basal ("primitive") avialan dinosaur known to date, and it is one of the earliest avialans found to date. The fossil evidence for the animal pre-dates that of Archaeopteryx lithographica , often considered the earliest bird species, by about 10 million years. [1] [2]
Aurornis xui was first described and named by Pascal Godefroit, Andrea Cau, Hu Dong-Yu, François Escuillié, Wu Wenhao and Gareth Dyke in 2013. The generic name is derived from the Latin word aurora, meaning "daybreak" or "dawn", and the Ancient Greek ὄρνις (órnis) meaning "bird". The specific name, A. xui, honors Xu Xing. [1] A recent study of specimens of the avialan Anchiornis has found that the traits exhibited by Aurornis fall within the range of variation in Anchiornis, warranting their synonymization. [3]
Aurornis was roughly the size of a modern pheasant, with a length of 50 cm (20 in). It had clawed wings and a long bony tail. Its leg bones were similar to those of Archaeopteryx, but overall its anatomy was more primitive. [2] Aurornis lived roughly 160 million years ago, roughly 10 million years before Archaeopteryx, which often has been described as the first bird. [2]
Aurornis was described from a sedimentary rock fossil in 2013. The fossil was purchased from a local dealer who said it had been unearthed in Yaoluguo in western Liaoning, China. Subsequent analysis confirmed it came from the Tiaojishan Formation, which has been dated to the late Jurassic period (Oxfordian stage), approximately 160 million years ago. [1] [4] [5] The fossil features traces of downy feathers along the animal's tail, chest, and neck. It was only partially prepared at the time of purchase with the feathers not showing, and bore no signs of forgery. [2]
On 7 June 2013, Science Magazine published an article that noted that Pascal Godefroit, the paleontologist who led the team that described Aurornis, reported that he is uncertain if the fossil material came from Liaoning province's 160-million-year-old Tiaojishan Formation, as the information provided by the fossil dealer indicated, or from the province's 125-million-year-old Yixian Formation, which is known to have produced several ancient bird fossils. [6] The failure to secure rigorous provenance information casts doubt on the claim that Aurornis is 160 million years old and predates Archaeopteryx . Godefroit's team will attempt to confirm the specimen's provenance, and its age, by conducting mineralogical and botanical analysis on the shale slab and then publishing their findings.
A 2017 study suggested that Aurornis may be a junior synonym of Anchiornis. [3]
A phylogenetic analysis of Aurornis published in 2013 found that it belongs in the bird lineage, in a more basal position than Archaeopteryx . [2] The analysis was based on "almost 1,500 [anatomical] characteristics." [7] On the other hand, a phylogenetic analysis conducted by Brusatte et al. (2014) recovered Aurornis outside Avialae; it was recovered as a troodontid closely related to Anchiornis , Xiaotingia and Eosinopteryx . [8] In 2017 re-evaluation of the Harlem Archaeopteryx specimen, Aurornis is found to be an anchiornithid. [9]
The classification of A. xui as a bird is somewhat contentious, however, due to the various differing definitions of the word "bird". Recent discoveries "[emphasize] how grey the dividing line is between birds and [non-avian] dinosaurs", says Paul Barrett of the Natural History Museum in London. "There's such a gradation in features between them that it's very difficult to tell them apart ... [Aurornis xui] is certainly an older member of the bird lineage than Archaeopteryx, and it's fair to call it a very primitive bird. But what you call a bird comes down to what you call a bird, and a lot of definitions depend on Archaeopteryx." [2] Bird evolution specialist Lawrence Witmer called the new analysis compelling, but said it remains difficult to distinguish birds from birdlike dinosaurs: "All of these little feathered species running and flapping around ... were all very similar." [10]
American paleontologist Luis Chiappe said that A. xui's forelimb is too short for this species to be a true bird. It "is very birdlike, but it is not yet a bird," he concluded. [11]
In his 2002 book Dinosaurs of the Air, Gregory S. Paul tried to conceptually model a "pro-avian". In his view, the direct ancestors of birds cannot have been completely arboreal, because in that case they would probably have used membranes to fly. He thought they must have represented an intermediate ecological stage, in which the hindlimbs still had largely cursorial adaptations whereas the arms had been elongated in order to climb. Feathers, originally serving the insulation of an already warm-blooded animal, would by elongation have turned the arms into wings in order to fly. More generally, the proavians would, in view of their basal theropod forebears and bird descendants, have been typified by long necks, a short trunk, long fingers with opposable digits, a decoupling of the locomotor functions of the forelimbs and hindlimbs, a lack of a propatagium, a shallow tail, and a weight of about one kilogramme. Paul illustrated his analysis with a skeletal diagram, accompanied by a life illustration of a "proavis". [12] When Aurornis was described in 2013, it was at the time the most basal known member of the Avialae, the group consisting of birds and their closest relatives. The Italian paleontologist Andrea Cau remarked it bore an uncanny resemblance to Paul's "proavis". [13] [14]
Archaeopteryx, sometimes referred to by its German name, "Urvogel" is a genus of bird-like dinosaurs. The name derives from the ancient Greek ἀρχαῖος (archaīos), meaning "ancient", and πτέρυξ (ptéryx), meaning "feather" or "wing". Between the late 19th century and the early 21st century, Archaeopteryx was generally accepted by palaeontologists and popular reference books as the oldest-known bird. Older potential avialans have since been identified, including Anchiornis, Xiaotingia, and Aurornis.
Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica, with fossilized teeth giving credence to the possibility that they inhabited Australia as well. This group of dinosaurs are known for their sickle-shaped toe claws and features in the shoulder bones.
Caudipteryx is a genus of small oviraptorosaur dinosaurs that lived in Asia during the Early Cretaceous, around 124.6 million years ago. They were feathered and extremely birdlike in their overall appearance, to the point that some paleontologists suggested it was a bird. Two species have been described: C. zoui, in 1998, and C. dongi, in 2000.
Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.
Jinfengopteryx is a genus of maniraptoran dinosaur. It was found in the Qiaotou Member of the Huajiying Formation of Hebei Province, China, and is therefore of uncertain age. The Qiaotou Member may correlate with the more well-known Early Cretaceous Yixian Formation, and so probably dates to around 122 Ma ago.
Yixianosaurus is a maniraptoran theropod dinosaur genus from the Early Cretaceous of China.
Scansoriopterygidae is an extinct family of climbing and gliding maniraptoran dinosaurs. Scansoriopterygids are known from five well-preserved fossils, representing four species, unearthed in the Tiaojishan Formation fossil beds of Liaoning and Hebei, China.
Juravenator is a genus of small coelurosaurian theropod dinosaur, which lived in the area which would someday become the top of the Franconian Jura of Germany, about 151 or 152 million years ago. It is known from a single, juvenile specimen.
Archaeopterygidae is a group of paravian dinosaurs, known from the latest Jurassic and earliest Cretaceous of Europe. In most current classifications, it contains only the genera Archaeopteryx and Wellnhoferia. As its name suggests, Protarchaeopteryx was also once referred to this group, but most paleontologists now consider it an oviraptorosaur. Other referred genera, like Jurapteryx, Wellnhoferia, and "Proornis", are probably synonymous with Archaeopteryx or do not belong into this group. Jinfengopteryx was originally described as an archaeopterygid, though it was later shown to be a troodontid. A few studies have recovered Anchiornis and Xiaotingia to also be members of the Archaeopterygidae, though most subsequent analyses have failed to arrive at the same result. Uncertainties still exist, however, and it may not be possible to confidently state whether archaeopterygids are more closely related to modern birds or to deinonychosaurs barring new and better specimens of relevant species. Teeth attributable to archaeopterygids are known from the earliest Cretaceous (Berriasian) Cherves-de-Cognac locality and the Angeac-Charente bonebed of France.
Yandangornis is a genus of theropods from the Late Cretaceous Tangshang Formation of China. It lived 81.5 million years ago in what is now China. The type species, Y. longicaudus, was formally described by Cai and Zhou in 1999.
Maniraptoriformes is a clade of dinosaurs with pennaceous feathers and wings that contains ornithomimosaurs and maniraptorans. This group was named by Thomas Holtz, who defined it as "the most recent common ancestor of Ornithomimus and birds, and all descendants of that common ancestor."
Avialae is a clade containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally used.
Paraves are a widespread group of theropod dinosaurs that originated in the Middle Jurassic period. In addition to the extinct dromaeosaurids, troodontids, anchiornithids, and possibly the scansoriopterygids, the group also contains the avialans, which include diverse extinct taxa as well as the over 10,000 species of living birds. Basal members of Paraves are well known for the possession of an enlarged claw on the second digit of the foot, which was held off the ground when walking in some species. A number of differing scientific interpretations of the relationships between paravian taxa exist. New fossil discoveries and analyses make the classification of Paraves an active subject of research.
Epidexipteryx is a genus of small paravian dinosaurs, known from one fossil specimen in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. Epidexipteryx represents the earliest known example of ornamental feathers in the fossil record.
Anchiornis is a genus of small, four-winged paravian dinosaurs, with only one known species, the type species Anchiornis huxleyi, named for its similarity to modern birds. The Latin name Anchiornis derives from a Greek word meaning "near bird", and huxleyi refers to Thomas Henry Huxley, a contemporary of Charles Darwin.
Xiaotingia is a genus of anchiornithid theropod dinosaur from Middle Jurassic or early Late Jurassic deposits of western Liaoning, China, containing a single species, Xiaotingia zhengi.
Eosinopteryx is an extinct genus of theropod dinosaurs known to the Late Jurassic epoch of China. It contains a single species, Eosinopteryx brevipenna.
Serikornis is a genus of small, feathered anchiornithid dinosaur from the Upper Jurassic Tiaojishan Formation of Liaoning, China. It is represented by the type species Serikornis sungei.
Anchiornithidae is a family of small paravian dinosaurs. Anchiornithids have been classified at varying positions in the paravian tree, with some scientists classifying them as a distinct family, a basal subfamily of Troodontidae, members of Archaeopterygidae, or an assemblage of dinosaurs that are an evolutionary grade within Avialae or Paraves.