''Zhenyuanlong'' (meaning ''"Zhenyuan's dragon"'', from
Chinese
Chinese can refer to:
* Something related to China
* Chinese people, people of Chinese nationality, citizenship, and/or ethnicity
**''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation
** List of ethnic groups in China, people of va ...
Pinyin
Hanyu Pinyin (), often shortened to just pinyin, is the official romanization system for Standard Mandarin Chinese in China, and to some extent, in Singapore and Malaysia. It is often used to teach Mandarin, normally written in Chinese for ...
龙/
龍 lóng ''"dragon"'') is a genus of
dromaeosaurid
Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
from the
Yixian Formation of
Liaoning
Liaoning () is a coastal province in Northeast China that is the smallest, southernmost, and most populous province in the region. With its capital at Shenyang, it is located on the northern shore of the Yellow Sea, and is the northernmost ...
,
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
. It lived during the
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...
age of the
early
Early may refer to:
History
* The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.:
** Early Christianity
** Early modern Europe
Places in the United States
* Early, Iowa
* Early, Texas
* Early ...
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
period, approximately 125 million years ago. It is known from a single specimen belonging to the species ''Zhenyuanlong suni'' (Chinese: 孫氏振元龍). This
type specimen
In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...
preserved a nearly complete skeleton that contains traces of feathers, including long tail feathers and large wings. In addition to further complicating diversity of Liaoning dromaeosaurids, this specimen provides the first evidence of well-developed
pennaceous
The pennaceous feather is a type of feather present in most modern birds and in some other species of maniraptoriform dinosaurs.
Description
A pennaceous feather has a stalk or quill. Its basal part, called a ''calamus'', is embedded in the skin ...
feathers in a large, non-flying dromaeosaur, raising the question of what function such wings would serve.
Discovery
The specimen was found by a local farmer near
Sihedang in
Jianchang
Jianchang () is a county of Huludao City in the southwest of Liaoning province, China. It is the largest division of Huludao, with an area of , and population of 600,000, located in mountainous terrain west of that city, serviced by China Natio ...
,
Liaoning Province
Liaoning () is a coastal provinces of China, province in Northeast China that is the smallest, southernmost, and most populous province in the region. With its capital at Shenyang, it is located on the northern shore of the Yellow Sea, and i ...
and was later secured for study at the
Jinzhou Paleontological Museum
Jinzhou (, ), formerly Chinchow, is a coastal prefecture-level city in central-west Liaoning province, China. It is a geographically strategic city located in the Liaoxi Corridor, which connects most of the land transports between North China ...
by Zhenyuan Sun, a representative of the museum.
There it was further prepared by Zhang Y.-Q. In 2015, the
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
''Zhenyuanlong suni'' was named and described by paleontologists
Lü Junchang of the
Chinese Academy of Geological Sciences
The Chinese Academy of Geological Sciences (CAGS; ) is an institution that engages in geoscience research in the People's Republic of China. The academy was established in 1956 and reorganized in 1999. Administratively it is under the PRC Ministry ...
in
Beijing
}
Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...
and
Stephen Brusatte of the
University of Edinburgh
The University of Edinburgh ( sco, University o Edinburgh, gd, Oilthigh Dhùn Èideann; abbreviated as ''Edin.'' in post-nominals) is a public research university based in Edinburgh, Scotland. Granted a royal charter by King James VI in 15 ...
in the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
. The generic name combines Zhenyuan Sun's
given name
A given name (also known as a forename or first name) is the part of a personal name quoted in that identifies a person, potentially with a middle name as well, and differentiates that person from the other members of a group (typically a fa ...
with the Chinese Pinyin ''long'', meaning "dragon". The
specific name Specific name may refer to:
* in Database management systems, a system-assigned name that is unique within a particular database
In taxonomy, either of these two meanings, each with its own set of rules:
* Specific name (botany), the two-part (bino ...
refers to his family name.
[ ''Zhenyuanlong'' was one of eighteen dinosaur taxa from 2015 to be described in open access or free-to-read journals.]
The holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
, JPM-0008, was found in the Sihedang locality of Jianchang County of northeastern China's Yixian Formation, which dates from the Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...
age
Age or AGE may refer to:
Time and its effects
* Age, the amount of time someone or something has been alive or has existed
** East Asian age reckoning, an Asian system of marking age starting at 1
* Ageing or aging, the process of becoming older ...
of the Early Cretaceous (125–113 million years ago). The holotype specimen is represented by its sub-adult status, its nearly complete and articulated skeleton lacking only half of the tail, its well preserved skull and lower jaws, and its preservation of vaned feathers on the arms and tail. The fossil is compressed on its stone plate or slab. A counterplate is absent.[
]
Description
''Zhenyuanlong suni'' was a mid-sized dromaeosaurid comparable in length to the similar ''Tianyuraptor
''Tianyuraptor'' is a genus of short-armed dromaeosaurid dinosaur ('running lizard'; a type of small dinosaur considered to be closely related to birds) that lived during the Early Cretaceous, about 122 million years ago. Its remains have been ...
''. The fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
skeleton is nearly complete but lacks the last half of the tail, giving the specimen a preserved length of . Based on comparison to the complete skeleton of ''Tianyuraptor'', it has been estimated that the skeleton of ''Zhenyuanlong'' would have been about long when complete. With the added length of long tail feathers, the animal was perhaps up to in life.[ The fossil represents a subadult individual, as shown by the fusion of the neural arches having been progressed into the ]sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
.[
Its overall proportions are comparable to ''Tianyuraptor'', a dromaeosaurid from the same formation, and it bears many anatomical similarities to the other Liaoning dromaeosaurids. The skull is well-preserved and similar in shape to that of ''Tianyuraptor'' and the related '']Sinornithosaurus
''Sinornithosaurus'' (derived from a combination of Latin and Greek, meaning 'Chinese bird-lizard') is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period (late Barremian) of the Yixian Formation in what is now China. It ...
''. Its sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
consists of six vertebrae
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...
, four of which are clearly fused, and its tail includes the network of bony support rods typical of dromaeosaurs, as well as middle caudal (tail) vertebrae that are somewhat elongated compared to most other dromaeosaurs. Both pectoral girdles are preserved and the specimen shows non-fused sternal plates
The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Shap ...
. Its leg proportions are similar to other Liaoning dromaeosaurs, with its tibiotarsus
The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia.
A similar structure also occurred in the Mesozoic Heterodontosauridae. These sm ...
longer than the femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
at a ratio of around 1.30. This large ratio is typical of Liaoning dromaeosaurs but differs from most other dinosaurs in this group.[
]
''Zhenyuanlong'' had very short arms and the shortest arm-to-leg length ratio of any known dromaeosaurid except for the basal
Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''.
Science
* Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure
* Basal (medicine), a minimal level that is nec ...
dromaeosaurid '' Mahakala'' and the giant unenlagiine ''Austroraptor
''Austroraptor'' ( ) is a genus of large dromaeosaurid dinosaur that lived during the Late Cretaceous Period in what is now Argentina.
''Austroraptor'' was a large-sized, moderately-built, ground-dwelling, bipedal carnivore, estimated at in len ...
''. Its arms also exhibit some unique and unusual features seen in few related dinosaurs. The radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
of ''Zhenyuanlongs forearm
The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anat ...
is among the proportionally thinnest of any theropod dinosaur, comparable only to a handful of basal coelurosaur
Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.
Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyrann ...
s and to alvarezsaur
Alvarezsauroidea is a group of small maniraptoran dinosaurs. Alvarezsauroidea, Alvarezsauridae, and Alvarezsauria are named for the historian Gregorio Álvarez, not the more familiar physicist Luis Alvarez, or his son geologist Walter Alvarez w ...
oids, which had extremely reduced arms and hands. ''Zhenyuanlong'' is also unique among Liaoning dromaeosaurids for its second metacarpal being shorter than the combined lengths of the first metacarpal and first bone of the innermost finger.[
]
Feathers
The type fossil of ''Zhenyuanlong'' preserves integument on several parts of the specimen, including a "hairy" coat of simple filaments over most of the body and large, vaned feathers on the tail and arms, which would have given the animal a life appearance indistinguishable from a bird. The body feathers of ''Zhenyuanlong'' are represented by small regions of imprints in the front and back of the neck. While poorly preserved, these feathers appear to contain small, simple filaments less than a millimeter thick and up to 30 millimeters long. Whether the animal's body feathers were simple and non-shafted or more complex filaments attaching to a central vane is impossible to determine from this specimen.[
]
Despite its small arms, the feathers that made up the wings were very long, more than twice the length of the humerus
The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
(upper arm). The wings were broad, with a total surface area of about one square meter each, but their precise shape is unknown due to taphonomic
Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov t ...
distortion. The specimen's right wing shows an overlapping complex of primary feathers (which attach to the second digit of the hand), secondary feathers (which attach to the forearm), and coverts
A covert feather or tectrix on a bird is one of a set of feathers, called coverts (or ''tectrices''), which, as the name implies, cover other feathers. The coverts help to smooth airflow over the wings and tail. Ear coverts
The ear coverts are sm ...
(which cover both sets). The overall feather architecture of the wings is similar to that of ''Microraptor
''Microraptor'' (Greek, μικρός, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. They dat ...
'', ''Changyuraptor
''Changyuraptor '' is a genus of "four-winged", predatory dinosaurs. It is known from a single fossil specimen representing the species ''Changyuraptor yangi'', which was discovered from Early Cretaceous (125 million year old) deposits in Liaoni ...
'', '' Anchiornis'', '' Eosinopteryx'', and basal avialans
Avialae ("bird wings") 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 ...
like ''Archaeopteryx
''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
'', but the coverts are noteworthy for being more similar in size and shape to these feathers in modern birds. These are preserved as a row of approximately 30 feathers of a consistent small size that attach perpendicularly to the ulna and third metacarpal of the specimen. The coverts of ''Archaeopteryx'' and other basal paravian
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 aviala ...
s that preserve them are, by contrast, considerably longer and cover much of the wing.[
The specimen's better-preserved right wing shows that the primary feathers were longer than its secondaries, and the authors estimate approximately 10 primaries and 20 secondaries. An asymmetric shape, as in modern birds, may be visible on some of both primaries and secondaries, but preservational distortion makes it difficult to assess this for certain. Overall, the shape and feather architecture of ''Zhenyuanlongs wings were most similar to those of ''Microraptor'', though the former lacks any sign of the alula feathers which attach to the first finger in modern birds and possibly ''Microraptor''.][
]
Long vaned feathers were also present along the length of the tail, and are preserved as a series of long projections of vanes at a 45-degree angle from the tail vertebrae. While preservation makes symmetry difficult to assess, these feathers appear generally similar to the tail feathers of other birdlike dinosaurs that preserve this region, including ''Sinornithosaurus'', ''Jinfengopteryx
''Jinfengopteryx'' (from , 'golden phoenix', the queen of birds in Chinese folklore, and grc, πτερυξ , meaning 'feather') is a genus of maniraptoran dinosaur. It was found in the Qiaotou Member of the Huajiying Formation of Hebei Province, ...
'', ''Anchiornis'', ''Eosinopteryx'', and ''Archaeopteryx''. This differentiates the tail of ''Zhenyuanlong'' from ''Microraptor'' and the related ''Changyuraptor
''Changyuraptor '' is a genus of "four-winged", predatory dinosaurs. It is known from a single fossil specimen representing the species ''Changyuraptor yangi'', which was discovered from Early Cretaceous (125 million year old) deposits in Liaoni ...
'', which had shorter feathers along the base and middle of the tail but large, complex fans at the tip. However, since the end of ''Zhenyuanlongs tail is not preserved, it's impossible to rule out the presence of a fan entirely.[
Given the close affinity of ''Zhenyuanlong'' with ''Microraptor'', ''Changyuraptor'' and ''Sinornithosaurus'', it is noteworthy that the specimen does not preserve any feathers on the hind limbs. Some of its closest relatives are known for long, voluminous vaned feathers attaching to the ankles and lower legs, and ''Zhenyuanlongs lack of similar feathers may indicate another unique anatomical feature of this animal among its relatives. However, the specimen's hind limbs belong to a piece of slab that preserves no other feathers on the body, while the other pieces all preserve feathers. Therefore, the lack of leg-feathers on ''Zhenyuanlong'' may be an artifact of preservation or preparation and, like the presence of a tail fan, cannot be ruled out with certainty.][
]
Paleobiology
At around 2 metres in length and covered in complex feathers, ''Zhenyuanlong'' would have been virtually indistinguishable from a large bird in life, and has been compared to a turkey
Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a list of transcontinental countries, transcontinental country located mainly on the Anatolia, Anatolian Peninsula in Western Asia, with ...
, emu
The emu () (''Dromaius novaehollandiae'') is the second-tallest living bird after its ratite relative the ostrich. It is endemic to Australia where it is the largest native bird and the only extant member of the genus ''Dromaius''. The emu' ...
, or "big chicken", with wings similar to those of an eagle
Eagle is the common name for many large birds of prey of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagle are from Eurasia and Africa. Outside this area, just ...
or vulture
A vulture is a bird of prey that scavenges on carrion. There are 23 extant species of vulture (including Condors). Old World vultures include 16 living species native to Europe, Africa, and Asia; New World vultures are restricted to North and ...
.[
] Its size would have been just over that of a modern condor, but it would have been at least twice as heavy at an estimated .[ Despite the modern-looking wings, due to this size and weight the animal was unlikely to be able to "fly or glide or do anything in the air".][
]
''Zhenyuanlong'' is considered by its authors to be a "rare and aberrant animal" compared to the related group of Liaoning dromaeosaurids to which it belongs, due to its large body size and short arms. It is the first demonstration of feather morphology in a short-armed dromaeosaurid, and is currently the largest known non-avian dinosaur with complex wings. Though the authors state that the animal is likely too big to fly, they also stress the importance of biomechanical modeling before drawing specific conclusions about the aerodynamic function (or lack thereof) of ''Zhenyuanlongs wings.[
This raises the question of what such a large, short-armed animal was doing with complex wings and feathers so similar to those used for flight in other animals. One possibility is that ''Zhenyuanlong'' is secondarily flightless, having a shared ancestry with smaller, potentially volant dromaeosaurids like ''Microraptor'' and then retaining aspects of flight capability through inertia or unknown adaptive reasons.][ Other possibilities include the use of wings in displaying to mates or rivals, protecting eggs in its nest, or even some amount of arboreal gliding.][ So-called "]wing-assisted incline running
Wing-assisted incline running (abbreviated as "WAIR") is a running behavior observed in living birds as well as a model proposed to explain the evolution of avian flight. WAIR allows birds to run up steep or vertical inclines by flapping their win ...
", which some modern birds use to help "flap" up steep inclines, is one potential aerodynamic use of ''Zhenyuanlongs wings.[ According to the authors and other paleontologists, the most viable hypothesis at this time is the use of the wings in sexual display, either to threaten rivals or to court potential mates, much as a peacock uses its tail to impress hens.][
Regardless of what practical function ''Zhenyuanlongs wings may have served, its discovery has provided a new glimpse into the diversity of Liaoning dromaeosaurid body plans and to the diversity of the Jehol Biota more generally. Despite the fact that the six Liaoning dromaeosaurids are spread across two formations (Yixian and Jiufotang) and therefore might not have all been contemporaneous, it is still the case that large-bodied, short-armed dromaeosaurids like ''Zhenyuanlong'' must have been coexisting with some of the smaller, long-armed ones, much as ecosystems support multiple species of birds today.][
]
Classification
''Zhenyuanlong'' has been placed in the family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
Dromaeosauridae. The authors' cladistic analysis recovered it in the same position in the evolutionary tree as the other five Liaoning dromaeosaurids (''Changyuraptor'', ''Graciliraptor
''Graciliraptor'' (meaning "graceful thief") is a genus of theropod dinosaur from the early Cretaceous Period. It is a microraptorine dromaeosaurid.
The type species ''Graciliraptor lujiatunensis'' was first named and described in 2004 by Xu X ...
'', ''Microraptor'', ''Sinornithosaurus'', and ''Tianyuraptor'') and the Eudromaeosauria though their exact relationships could not be resolved. The cladogram below follows the analysis of the holotype by Lü & Brusatte 2015.[
It was noted that ''Zhenyuanlong'' did not necessarily form its own group or ]clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
with ''Tianyuraptor'', despite uniquely sharing short arms among the Liaoning dromaeosaurids, and nor did the Liaoning dromaeosaurids form their own clade. Instead, they resolved into a broad group that included eudromaeosaurs, which in turn includes the Laurasia
Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pan ...
n Dromaeosaurinae and Velociraptorinae subfamilies
In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
. This condition, where a node (which represents a shared ancestor) begets multiple immediate branches that don't cluster into further groups, is known as a polytomy and reflects phylogenetic uncertainty. The uncertainty in the case of ''Zhenyuanlong'' is a result of homoplasy induced by introduction of the new genus. This means that ''Zhenyuanlong'' possesses a "hodge-podge" of character
Character or Characters may refer to:
Arts, entertainment, and media Literature
* ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk
* ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to The ...
s shared with a number of disparate dromaeosaurids. For example, ''Zhenyuanlong'' shares its short arm morphology with ''Tianyuraptor'', but other features with dromaeosaurids that are not closely related to ''Tianyuraptor''.[
The result is that it is not yet possible to know precisely where ''Zhenyuanlongs closest phylogenetic affinities lie. There may exist a clade of Liaoning dromaeosaurids that includes a smaller group of short-armed dromaeosaurids, or short arms may have evolved multiple times in this group.][
]
See also
* Timeline of dromaeosaurid research
References
{{Taxonbar, from=Q20670696
Early Cretaceous dinosaurs of Asia
Yixian fauna
Dromaeosaurs
Fossil taxa described in 2015
Feathered dinosaurs
Taxa named by Stephen L. Brusatte
Taxa named by Lü Junchang