''Yutyrannus'' (meaning "feathered tyrant") is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
proceratosaurid tyrannosauroid
Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...
dinosaur which contains a single known
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
, ''Yutyrannus huali''. This species lived during the 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 in what is now northeastern
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 ...
.
[ Three ]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 ...
s of ''Yutyrannus huali'' —all found in the rock beds 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 ...
Province— are currently the largest-known carnivorous dinosaur specimens that preserve direct evidence of feather
Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and a premier ...
s.
Discovery and naming
''Yutyrannus huali'' was named and scientifically described in 2012 by Xu Xing ''et al.'' The name is derived from Mandarin Chinese
Mandarin (; ) is a group of Chinese (Sinitic) dialects that are natively spoken across most of northern and southwestern China. The group includes the Beijing dialect, the basis of the phonology of Standard Chinese, the official language of ...
''yǔ'' (羽, "feather") and Latinised Greek ''tyrannos'' (τύραννος, "tyrant"), a reference to its classification as a feathered member of the Tyrannosauroidea
Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...
. The specific name consists of the Mandarin ''huáli'' (华丽 simplified, 華麗 traditional, "beautiful"), in reference to the perceived beauty of the plumage
Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
.[
''Yutyrannus'' is known from three nearly complete fossil specimens (an adult, a subadult and a juvenile) acquired from a fossil dealer who claimed all three had their provenance in a single quarry at Batu Yingzi in ]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 ...
Province, China. They were thus probably found in a layer of the Yixian Formation
The Yixian Formation (; formerly transcribed as Yihsien Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the late Barremian and early Aptian stages of the Early Cretaceous. It is known for its ex ...
, dating 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 ...
, approximately 125 million years old.[ The specimens had been cut into pieces about the size of bath mats, which could be carried by two people.][ (with illustrations)]
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 ...
, ZCDM V5000, is the largest specimen, consisting of a nearly complete skeleton with skull, compressed on a slab, of an adult individual. The paratype
In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). Of ...
s are the two other specimens: ZCDM V5001 consisting of a skeleton of a smaller individual and part of the same slab as the holotype; and ELDM V1001, a juvenile estimated to have been eight years younger than the holotype. The fossils are part of the collections of the Zhucheng Dinosaur Museum and the Erlianhaote Dinosaur Museum but have been prepared by the Institute of Vertebrate Paleontology and Paleoanthropology The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name suggest ...
, under the guidance of Xu.
Description
''Yutyrannus'' was a large bipedal
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...
predator. The holotype and oldest-known specimen has an estimated length of and an estimated weight of about .[ In 2016, ]Gregory S. Paul
Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dino ...
gave lower estimations of and . Its skull has an estimated length of . The skulls of the paratypes are and long and their weights have been estimated at and , respectively.[
]
The describers established some diagnostic traits of ''Yutyrannus'', in which it differs from its direct relatives. The snout features a high midline crest, formed by the nasals
In phonetics, a nasal, also called a nasal occlusive or nasal stop in contrast with an oral stop or nasalized consonant, is an occlusive consonant produced with a lowered velum, allowing air to escape freely through the nose. The vast majorit ...
and the premaxilla
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...
e and which is covered by large pneumatic recesses. The postorbital bone
The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some v ...
has a small secondary process, jutting into the upper hind corner of the eye socket. The outer side of the main body of the postorbital is hollowed out. In the lower jaw, the external mandibular fenestra, the main opening in the outer side, is mainly located in the surangular
The suprangular or surangular is a jaw bone found in most land vertebrates, except mammals. Usually in the back of the jaw, on the upper edge, it is connected to all other jaw bones: dentary, angular, splenial and articular. It is often a mu ...
.[
According to a 2018 study, ''Yutyrannus'' had a simple ]hyoid
The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebra. ...
structure, indicating it had a flat tongue
The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...
, like a crocodile
Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...
. Based on hyoid bone comparisons between living and extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
archosaurs
Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avi ...
, it was determined that all archosaurs would have had fixed tongues, with the exception of birds
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
, pterosaurs
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...
and certain ornithischians
Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...
.
Feathers
The described specimens of ''Yutyrannus'' contain direct evidence of feathers in the form of fossil imprints. The feathers were long, up to , and filamentous. Because the quality of the preservation was low, it could not be established whether the filaments were simple or compound, broad or narrow. The feathers covered various parts of the body. With the holotype they were present on the pelvis and near the foot. Specimen ZCDM V5000 had feathers on the tail pointing backwards under an angle of 30 degrees with the tail axis. The smallest specimen showed filaments on the neck and feathers at the upper arm.[ While it has been known since 2004, upon the description of '']Dilong
''Dilong'' (; lit. "earth dragon") is a Chinese dragon name that is also used to mean "earthworm" in traditional Chinese medicine and '' Geosaurus'' in zoological nomenclature.
Dragon
In Chinese mythology, ''dilong'' "earth dragon" is one of ...
'', that at least some tyrannosauroids possessed filamentous "stage 1" feathers, according to the feather typology of Richard Prum
Richard O. Prum (born 1961) is William Robertson Coe Professor of ornithology, and head curator of vertebrate zoology at the Peabody Museum of Natural History at Yale University.
Life and work
Prum describes himself as "an evolutionary ornithol ...
, ''Y. huali'' is currently the largest-known species of dinosaur with direct evidence of feathers, forty times heavier than the previous record holder, '' Beipiaosaurus''.
Based on the distribution of the feathers, they may have covered the whole body and served in regulating temperature, given the rather cold climate of the Yixian with an average annual temperature of . Alternatively, if they were restricted to the regions in which they were found, they may have served as display structures. In addition, the two adult specimens had distinctive, "wavy" crests on their snouts, on both sides of a high central crest, which were probably used for display. The presence of feathers on a large basal tyrannosauroid suggests the possibility that later tyrannosaurids were also feathered, even when adult, despite their size.[ However, scaly skin impressions have been reported from various Late Cretaceous tyrannosaurids (such as '']Gorgosaurus
''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.6 and 75.1 million years ago. Fossil remains have been found in the Can ...
'', ''Tarbosaurus
''Tarbosaurus'' ( ; meaning "alarming lizard") is a genus of tyrannosaurid dinosaur that flourished in Asia about 70 million years ago, at the end of the Late Cretaceous Period, considered to contain a single known species, ''Tarbosaurus ba ...
'' and ''Tyrannosaurus
''Tyrannosaurus'' is a genus of large theropoda, theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosa ...
'') on parts of the body where ''Yutyrannus'' was feathered. Since there is no positive evidence for plumage in tyrannosaurids, some researchers have suggested they may have evolved scales secondarily.[Switek, B. 2013]
Palaeontology: The truth about ''T. rex''.
''Nature News'', 23 October 2013. If scaly skin was the dominant epidermal trait of later genera, then the extent and nature of the integumentary covering may have changed over time in response to body size, a warmer climate, or other factors.[
It's possible that the integumentary structures of ''Yutyrannus'' might not represent true feathers and represent filamentous structures, being ancestral state to feathers.]
Classification
To date, all phylogenetic analyses
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
of ''Yutyrannus'' relationships have classified it in the group Tyrannosauroidea
Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...
. An initial analysis of its relationship to other tyrannosauroids showed that it was more primitive than ''Eotyrannus
''Eotyrannus'' (meaning "dawn tyrant") is a genus of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom. The r ...
'' in the evolutionary tree, but more advanced than tyrannosauroids such as ''Dilong'', ''Guanlong
''Guanlong'' (冠龍) is a genus of extinct proceratosaurid tyrannosauroid from the Late Jurassic of China. The taxon was first described in 2006 by Xu Xing ''et al.'', who found it to represent a new taxon related to ''Tyrannosaurus''. The na ...
'' and ''Sinotyrannus
''Sinotyrannus'' (meaning "Chinese tyrant") is a genus of large basal tyrannosauroid dinosaur, known from a single incomplete fossil specimen including a partial skull, from the Early Cretaceous Jiufotang Formation of Liaoning, China. Specifi ...
''. Primitive traits relative to advanced tyrannosaurs included long forelimbs with three fingers and a short foot which was not specialized for running. Advanced traits included a large and deep skull, the outer side of the premaxilla having rotated upwards, a large cuneiform horn on the lacrimal in front of the eye socket, a postorbital process on the back rim of the eye socket, the squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone.
In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...
and the quadratojugal The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians.
Anatomy and function
In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...
forming a large process on the back rim of the infratemporal fenestra
An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit in some animals. It is ventrally bordered by a zygomatic arch. An opening in front of the eye sockets ...
, short dorsal vertebrae, an ilium with a straight upper rim and an appending lobe, a large pubic foot and a slender .[
]
In 2016, a phylogenetic analysis conducted by Thomas Carr and Stephen Brusatte re-examined the evolutionary relationships of the Tyrannosauroidea. Their analysis found ''Yutyrannus'' to be more basal than ''Dilong'', placing it within the family Proceratosauridae
Proceratosauridae is a Family (biology), family or clade of Tyrannosauroidea, tyrannosauroid theropod dinosaurs from the Middle Jurassic to the Early Cretaceous.
Distinguishing features
Unlike the advanced Tyrannosauridae, tyrannosaurids but s ...
.[Brusatte, S.L. and Carr, T.D. 2016]
The phylogeny and evolutionary history of tyrannosauroid dinosaurs.
''Scientific Reports'', 6(20252). Their cladogram is shown below:
Paleobiology
The knowledge of specimens representing various different ages has allowed paleontologists to determine the ontogeny
Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the stu ...
, or change during growth, of this species. During growth the lower legs, feet, ilia and forelimbs became relatively smaller. The skull, on the other hand, grew more robust and deeper.[
]
Paleoecology
Because the three known individuals of ''Yutyrannus'' were allegedly found together, some paleontologists, including Xu Xing, have interpreted the animal as a pack hunter. Based on the presence of sauropod
Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...
material in the quarry in which the three specimens were found, Xu has further speculated that ''Yutyrannus'' may have hunted sauropods, and that the three known individuals may have died while doing so. In addition, other sauropod hunting theropods such as ''Mapusaurus'' are known to have exhibited pack hunting behaviour. The true cause of their death, however, remains unknown.[ If ''Yutyrannus'' did prey on sauropods, it would have been one of two predatory animals known from the Yixian formation capable of doing so, the other being an as-of-yet undescribed large theropod known from a tooth embedded in the rib of a ''Dongbeititan''.][Xing L., Bell, P.R., Currie, P.J., Shibata M., Tseng K. & Dong Z. (2012). "A sauropod rib with an embedded theropod tooth: direct evidence for feeding behaviour in the Jehol group, China." ''Lethaia'', (advance online publication). .]
Because the locality of ''Yutyrannus'' is uncertain, it is unknown what fauna it coexisted with. Age estimates point towards ''Yutyrannus'' originating from the Lujiatun or the Jianshangou beds of the Yixian, meaning it would have been contemporaneous of such dinosaurs as ''Psittacosaurus
''Psittacosaurus'' ( ; "parrot lizard") is a genus of extinct ceratopsian dinosaur from the Early Cretaceous of what is now Asia, existing between 126 and 101 million years ago. It is notable for being the most species-rich non-avian dinosaur gen ...
'', ''Dongbeititan
''Dongbeititan'' is a genus of sauropod dinosaur from the Early Cretaceous-age Yixian Formation of Beipiao, Liaoning, China. It is based on holotype DNHM D2867, a partial postcranial skeleton including bones from the limbs, shoulder and pelvic gi ...
'', ''Sinosauropteryx
''Sinosauropteryx'' (meaning "Chinese reptilian wing", ) is a compsognathid dinosaur. Described in 1996, it was the first dinosaur taxon outside of Avialae (birds and their immediate relatives) to be found with evidence of feathers. It was cover ...
'', and ''Caudipteryx
''Caudipteryx'' (which means "tail feather") is a genus of peacock-sized theropod dinosaurs that lived in the Barremian age of the early Cretaceous (about 124.6 million years ago). They were feathered and extremely birdlike in their overall appea ...
''. Fish such as ''Lycoptera
''Lycoptera'' is an extinct genus of fish that lived from the late Jurassic to Cretaceous periods in present-day China, North Korea, Mongolia and Siberia. It is known from abundant fossils representing sixteen species, which serve as important ind ...
'' would also have been prevalent. Volcanic eruptions and forest fires appear to have been common in the Yixian, and the environment would have been littered with bodies of water and coniferous plants. The environment would have been comparable to the modern day temperate rainforest
Temperate rainforests are coniferous or broadleaf forests that occur in the temperate zone and receive heavy rain.
Temperate rain forests occur in oceanic moist regions around the world: the Pacific temperate rain forests of North American Paci ...
s of British Columbia, and would have experienced significant seasonal changes in temperature.
See also
* Timeline of tyrannosaur research
This timeline of tyrannosaur research is a chronological listing of events in the history of paleontology focused on the tyrannosaurs, a group of predatory theropod dinosaurs that began as small, long-armed bird-like creatures with elaborate cr ...
References
External links
''T. rex'' relative is biggest-ever feathered animal
from BBC News
BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broadca ...
{{Taxonbar, from=Q131710
Early Cretaceous dinosaurs of Asia
Feathered dinosaurs
Fossil taxa described in 2012
Proceratosaurids
Taxa named by Xu Xing
Yixian fauna