Anchiornis
Encyclopedia
Anchiornis is a genus
of small, feathered, deinonychosaurian
dinosaur
. The genus Anchiornis contains the type species
Anchiornis huxleyi, named in honor of Thomas Henry Huxley, an early proponent of biological evolution
, and the first to propose a close evolutionary relationship between birds and dinosaurs. The generic name Anchiornis means "near bird", and its describers cited it as important in filling a gap in the transition between the body plans of avian
birds and non-avian dinosaurs.
Anchiornis fossils have been found in the Tiaojishan Formation
of Liaoning
, China
, dating somewhat uncertainly to the mid-late Jurassic
period (Callovian
or Oxfordian stage), 160 to 155 million years ago.
Given the exquisite preservation of one of the animal's fossils, Anchiornis became the first Mesozoic dinosaur for which almost the entire life coloration could be determined.
dinosaur with a triangular skull bearing several details in common with other deinonychosaurs. Anchiornis had very long legs, usually an indication that it was a strong runner (however, the extensive leg feathers indicate that this may be a vestigial trait, as running animals tend to have reduced, not increased, hair or feathers on their legs). The forelimbs of Anchiornis were also very long, similar to other archaeopterygids
and early birds
, emphasizing its basal ("primitive") position among its relatives.
The first fossil was recovered from the Yaolugou locality, Jianchang County
, western Liaoning
, China; the second, at the Daxishan locality of the same area. The deposits are lake sediment, and are of uncertain age. Radiological measurements indicate an early Late Jurassic
age for them, between 161 and 151 million years ago.
As in other early paravians
such as Microraptor
, Anchiornis had large wings, made up of pennaceous flight feather
s attached to the arm and hand (as in modern birds) as well as flight feathers on the hind legs, forming an arrangement of fore and hind wings. The forewing of Anchiornis was composed of 11 primary feathers and 10 secondary feathers. Unlike Microraptor, the primary feathers in Anchiornis were about as long as the secondaries and formed a more rounded wing, with curved but symmetrical central vanes, a small and thin relative size, and rounded tips, all indicating poorer aerodynamic ability compared to its later relative. In Microraptor and Archaeopteryx
, the longest forewing feathers were closest to the tip of the wing, making the wings appear long, narrow, and pointed. However, in Anchiornis, the longest wing feathers anchored near the wrist, making the wing broadest in the middle and tapering near the tip for a more rounded, less flight-adapted profile.
The hind wings of Anchiornis were also shorter than those of Microraptor, and were made up of 12–13 flight feathers anchored to the tibia (lower leg) and 10–11 to the metatarsus (upper foot). Also unlike Microraptor, the hind wing feathers were longest closer to the body, with the foot feathers being short and directed downward, almost perpendicular to the foot bones.
Unlike any other known Mesozoic dinosaur, the feet of Anchiornis (except for the claws) were completely covered in feathers (much shorter than the ones making up the hind wing).
Two types of simpler, downy
(plumaceous) feathers covered the rest of the body, as in Sinornithosaurus
. Long downy feathers covered almost the entire head and neck, torso, upper legs, and the first half of the tail. The rest of the tail bore pennaceous tail feathers (rectrices).
), Anchiornis became the first Mesozoic dinosaur for which almost the entire life coloration was known (note that the tail of this specimen was not preserved).
Most of the body feathers of Anchiornis were gray and black. The crown of head feathers was mainly rufous
with a gray base and front, and the face had rufous speckles among predominantly black head feathers. The fore and hind wing feathers were white with black tips. The coverts (shorter feathers covering the bases of the long wing feathers) were gray, contrasting the mainly white main wings. The larger coverts of the wing were also white with gray or black tips, forming rows of darker dots along mid-wing. These took the form of dark stripes or even rows of dots on the outer wing (primary feather coverts) but a more uneven array of speckles on the inner wing (secondary coverts). The shanks of the legs were gray other than the long hind wing feathers, and the feet and toes were black.
, and the authors pointed out that long forelimbs are necessary for flight. Anchiornis also had a more avian wrist than other non-avialan theropods. The authors initially speculated that it would have been possible for Anchiornis to fly or glide. However, further finds showed that the wings of Anchiornis, while well-developed, were short when compared to later species like Microraptor
, with relatively short primary feathers that had rounded, symmetrical tips, unlike the pointed, aerodynamically proportioned feathers of Microraptor.
Anchiornis has hind leg proportions more like those of lower theropod dinosaurs than avialans, with long legs indicating a fast-running lifestyle. However, while long legs normally indicate a fast runner, the legs and even feet and toes of Anchiornis were covered in feathers, including long flight feathers similar to those in the hind wings of Microraptor, making it unlikely that Anchiornis was a capable ground runner.
Like many modern birds, Anchiornis exhibited a complex pattern of coloration with different colors in speckled patterns across the body and wings, or "within- and among-feather plumage coloration." In modern birds, such color patterning is used in communication and display, either to members of the same species (e.g. for mating or territorial threat display) or to threaten and warn off competing or predatory species.
, specimen number IVPP V14378) was described by paleontologist Xu Xing and colleagues in a paper accepted to the Chinese Science Bulletin
in 2009. Xu et al. assigned Anchiornis to the Avialae
in this paper. The specimen consists of an articulated skeleton missing only the skull, part of the tail, and the right forelimb. The authors estimated that a complete individual would be 34 cm (13.4 in) and weigh only 110 g (3.9 oz), making it the smallest known non-avialan dinosaur. (See also Shortest non-avian theropods and Least massive non-avian theropods).
A second specimen was reported on September 24, 2009, in the journal Nature
. It is catalogued as number in the Liaoning Paleontological Museum. It is larger and much more complete and preserves long wing feathers on the hands, arms, legs and feet, not unlike Microraptor
. There is also a feathered crest on the head. This second specimen preserves more features, and led Hu and colleagues to reassign Anchiornis to the Troodontidae
. A third specimen, preserving a nearly complete skeleton missing the tail and a partial skull, also with extensive feather preservation, was reported in 2010. This third specimen was used to determine the life coloration. It is housed in the Beijing Museum of Natural History
with the specimen number BMNHC PH828.
While only three specimens have been formally described, many more have been identified and are held in both private collections and museums. The Shandong Tianyu Museum of Nature in Pingyi County
, China, for example, was reported to hold 255 specimens of Anchiornis in its collections in 2010.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of small, feathered, deinonychosaurian
Deinonychosauria
The Deinonychosauria were a clade of coelurosaurian theropod dinosaurs from the Late Jurassic and Cretaceous periods. These omnivores and carnivores are known for their switchblade-like second toe claws and for displaying numerous bird-like characteristics. The clade has been divided into two...
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...
. The genus Anchiornis contains the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
Anchiornis huxleyi, named in honor of Thomas Henry Huxley, an early proponent of biological evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
, and the first to propose a close evolutionary relationship between birds and dinosaurs. The generic name Anchiornis means "near bird", and its describers cited it as important in filling a gap in the transition between the body plans of avian
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...
birds and non-avian dinosaurs.
Anchiornis fossils have been found in the Tiaojishan Formation
Tiaojishan Formation
The Tiaojishan Formation is a geological formation in Hebei and Liaoning, People's Republic of China, dating to the middle-late Jurassic period . It is known for its fossil plants, and is made up mainly of pyroclastic rock interspersed with basic volcanic and sedimentary rocks...
of Liaoning
Liaoning
' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, dating somewhat uncertainly to the mid-late Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
period (Callovian
Callovian
In the geologic timescale, the Callovian is an age or stage in the Middle Jurassic, lasting between 164.7 ± 4.0 Ma and 161.2 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian....
or Oxfordian stage), 160 to 155 million years ago.
Given the exquisite preservation of one of the animal's fossils, Anchiornis became the first Mesozoic dinosaur for which almost the entire life coloration could be determined.
Description
Anchiornis is a small, paravianParaves
Paraves is a branch-based clade containing birds and other closely related dinosaurs. The paravians include the Avialae, including Archaeopteryx and modern birds, and the Deinonychosauria, which includes the dromaeosaurids and troodontids....
dinosaur with a triangular skull bearing several details in common with other deinonychosaurs. Anchiornis had very long legs, usually an indication that it was a strong runner (however, the extensive leg feathers indicate that this may be a vestigial trait, as running animals tend to have reduced, not increased, hair or feathers on their legs). The forelimbs of Anchiornis were also very long, similar to other archaeopterygids
Archaeopterygidae
The Archaeopterygidae is a group of maniraptoran dinosaurs that lived during the late Jurassic and period.-Taxonomy:The order Archaeopterygiformes was coined by Max Fürbringer in 1888 to contain the single family Archaeopterygidae and genus Archaeopteryx...
and early birds
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
, emphasizing its basal ("primitive") position among its relatives.
The first fossil was recovered from the Yaolugou locality, Jianchang County
Jianchang County
Jianchang County is an administrative division within Huludao City in the southwest of Liaoning Province, in Northeast China. It is the largest division of Huludao, with an area of , and is located in mountainous terrain west of that city....
, western Liaoning
Liaoning
' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...
, China; the second, at the Daxishan locality of the same area. The deposits are lake sediment, and are of uncertain age. Radiological measurements indicate an early Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
age for them, between 161 and 151 million years ago.
Feathers
While the first specimen of Anchiornis preserved only faint traces of feathers around the preserved portion of the body, the well-preserved second specimen showed nearly complete feather preservation, allowing researchers to identify the structure of the feathers and how they were distributed.As in other early paravians
Paraves
Paraves is a branch-based clade containing birds and other closely related dinosaurs. The paravians include the Avialae, including Archaeopteryx and modern birds, and the Deinonychosauria, which includes the dromaeosaurids and troodontids....
such as Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...
, Anchiornis had large wings, made up of pennaceous flight feather
Flight feather
Flight feathers are the long, stiff, asymmetrically shaped, but symmetrically paired feathers on the wings or tail of a bird; those on the wings are called remiges while those on the tail are called rectrices . Their primary function is to aid in the generation of both thrust and lift, thereby...
s attached to the arm and hand (as in modern birds) as well as flight feathers on the hind legs, forming an arrangement of fore and hind wings. The forewing of Anchiornis was composed of 11 primary feathers and 10 secondary feathers. Unlike Microraptor, the primary feathers in Anchiornis were about as long as the secondaries and formed a more rounded wing, with curved but symmetrical central vanes, a small and thin relative size, and rounded tips, all indicating poorer aerodynamic ability compared to its later relative. In Microraptor and 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"...
, the longest forewing feathers were closest to the tip of the wing, making the wings appear long, narrow, and pointed. However, in Anchiornis, the longest wing feathers anchored near the wrist, making the wing broadest in the middle and tapering near the tip for a more rounded, less flight-adapted profile.
The hind wings of Anchiornis were also shorter than those of Microraptor, and were made up of 12–13 flight feathers anchored to the tibia (lower leg) and 10–11 to the metatarsus (upper foot). Also unlike Microraptor, the hind wing feathers were longest closer to the body, with the foot feathers being short and directed downward, almost perpendicular to the foot bones.
Unlike any other known Mesozoic dinosaur, the feet of Anchiornis (except for the claws) were completely covered in feathers (much shorter than the ones making up the hind wing).
Two types of simpler, downy
Down feather
The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator and padding, used in goods such as jackets, bedding,...
(plumaceous) feathers covered the rest of the body, as in Sinornithosaurus
Sinornithosaurus
Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999...
. Long downy feathers covered almost the entire head and neck, torso, upper legs, and the first half of the tail. The rest of the tail bore pennaceous tail feathers (rectrices).
Color
In 2010, a team of scientists examined numerous points among the feathers of an extremely well preserved Anchiornis specimen to survey the distribution of melanosomes, the pigment cells that give feathers their color. By studying the types of melanosomes and comparing them with those of modern birds, the scientists were able to map the specific colors and patterning present on Anchiornis when it was alive. Though this technique had been used and described for isolated bird feathers and portions of other dinosaurs (such as the tail of SinosauropteryxSinosauropteryx
Sinosauropteryx was the first genus of dinosaur outside of Avialae to be found with evidence of feathers. They were covered with "furry" coats of very simple filament-like feathers...
), Anchiornis became the first Mesozoic dinosaur for which almost the entire life coloration was known (note that the tail of this specimen was not preserved).
Most of the body feathers of Anchiornis were gray and black. The crown of head feathers was mainly rufous
Rufous
Rufous is a colour that may be described as reddish-brown or brownish-red, as of rust or oxidised iron.The first recorded use of rufous as a colour name in English was in the year 1782....
with a gray base and front, and the face had rufous speckles among predominantly black head feathers. The fore and hind wing feathers were white with black tips. The coverts (shorter feathers covering the bases of the long wing feathers) were gray, contrasting the mainly white main wings. The larger coverts of the wing were also white with gray or black tips, forming rows of darker dots along mid-wing. These took the form of dark stripes or even rows of dots on the outer wing (primary feather coverts) but a more uneven array of speckles on the inner wing (secondary coverts). The shanks of the legs were gray other than the long hind wing feathers, and the feet and toes were black.
Paleobiology
Anchiornis is notable for its proportionally long forelimbs, which measured 80% of the total length of the hind limbs. This is similar to the condition in early avians such as ArchaeopteryxArchaeopteryx
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"...
, and the authors pointed out that long forelimbs are necessary for flight. Anchiornis also had a more avian wrist than other non-avialan theropods. The authors initially speculated that it would have been possible for Anchiornis to fly or glide. However, further finds showed that the wings of Anchiornis, while well-developed, were short when compared to later species like Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...
, with relatively short primary feathers that had rounded, symmetrical tips, unlike the pointed, aerodynamically proportioned feathers of Microraptor.
Anchiornis has hind leg proportions more like those of lower theropod dinosaurs than avialans, with long legs indicating a fast-running lifestyle. However, while long legs normally indicate a fast runner, the legs and even feet and toes of Anchiornis were covered in feathers, including long flight feathers similar to those in the hind wings of Microraptor, making it unlikely that Anchiornis was a capable ground runner.
Like many modern birds, Anchiornis exhibited a complex pattern of coloration with different colors in speckled patterns across the body and wings, or "within- and among-feather plumage coloration." In modern birds, such color patterning is used in communication and display, either to members of the same species (e.g. for mating or territorial threat display) or to threaten and warn off competing or predatory species.
History of discovery
The type specimen (in the collection of the Institute of Vertebrate Paleontology and PaleoanthropologyInstitute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...
, specimen number IVPP V14378) was described by paleontologist Xu Xing and colleagues in a paper accepted to the Chinese Science Bulletin
Chinese Science Bulletin
The Chinese Science Bulletin is a scientific journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China...
in 2009. Xu et al. assigned Anchiornis to the Avialae
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
in this paper. The specimen consists of an articulated skeleton missing only the skull, part of the tail, and the right forelimb. The authors estimated that a complete individual would be 34 cm (13.4 in) and weigh only 110 g (3.9 oz), making it the smallest known non-avialan dinosaur. (See also Shortest non-avian theropods and Least massive non-avian theropods).
A second specimen was reported on September 24, 2009, in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
. It is catalogued as number in the Liaoning Paleontological Museum. It is larger and much more complete and preserves long wing feathers on the hands, arms, legs and feet, not unlike Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...
. There is also a feathered crest on the head. This second specimen preserves more features, and led Hu and colleagues to reassign Anchiornis to the Troodontidae
Troodontidae
Troodontidae is a family of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and scrappy and they have therefore been allied, at various times, with many dinosaurian lineages...
. A third specimen, preserving a nearly complete skeleton missing the tail and a partial skull, also with extensive feather preservation, was reported in 2010. This third specimen was used to determine the life coloration. It is housed in the Beijing Museum of Natural History
Beijing Museum of Natural History
The Beijing Museum of Natural History is located at 126, Tian Qiao Nan Street, Chong Wen District, Beijing, 100050, and is the most popular natural history museum in China. It was originally founded in 1951 as the National Central Museum of Natural History, and its name changed to the Beijing...
with the specimen number BMNHC PH828.
While only three specimens have been formally described, many more have been identified and are held in both private collections and museums. The Shandong Tianyu Museum of Nature in Pingyi County
Pingyi County
Pingyi County is a county under charge of Linyi City, Shandong Province of China. It has a land area of 1,824.79 square kilometers and a population of 980,000 in 2001. Its special local products are honeysuckle and granite...
, China, for example, was reported to hold 255 specimens of Anchiornis in its collections in 2010.
