Graciliraptor
Encyclopedia
Graciliraptor 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 Xing and Wang Xiaoling. The generic name is derived from Latin
gracilis and raptor. The specific name refers to the village Lujiatun where the fossil site is located. Its fossil
, holotype
IVPP V 13474, was found in Beipiao
, Liaoning Province, China
.
with some teeth, nearly complete fore and hind legs; and ten partial tail vertebrae. It is estimated to have been about 90 centimetres (3 ft) long in life. Graciliraptor is extremely lightly built for a non-avian theropod, with very elongated middle caudal vertebrae and lower leg bones. The femur
is thirteen centimetres long and total body length was estimated at one metre. The posterior articular processes of the tail vertebrae, or postzygapophyses, are connected by a thin bone sheath or lamina, that extends to the back over an eighth of the centrum of the following vertebra, thus further stiffening the middle tail, already immobilised by the typical dromaeosaurid long prezygapophyses.
Graciliraptor has been found in the lowest portions of the Yixian Formation
, the Lujiatun Member, below the rocks where similar early dromaeosaurids (such as Sinornithosaurus
and Microraptor
) were found. It is, in geological age, the oldest named dromaeosaurid, and the oldest known from good fossil remains (dromaeosaurid fossils date back all the way to the Middle Jurassic
, but consist mostly of teeth).
and avialan birds
, supporting a close relationship between avialans, troodontids, and dromaeosaurids.
Xu and Wang considered Graciliraptor to have been closely related to Microraptor
, a similar dromaeosaurid from the slightly younger Jiufotang Formation
. Later it was placed in the Microraptorinae
.
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 theropod 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...
from the early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period. It is a microraptorine
Microraptorinae
Microraptorinae is a subfamily of Dromaeosauridae. Microraptorines were among the most primitive dromaeosaurids. They appeared 125 million years ago in China. Many may have been semi-arboreal gliders...
dromaeosaurid
Dromaeosauridae
Dromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...
.
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...
Graciliraptor lujiatunensis was first named and described in 2004 by Xu Xing and Wang Xiaoling. The generic name is derived from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
gracilis and raptor. The specific name refers to the village Lujiatun where the fossil site is located. Its fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
, holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
IVPP V 13474, was found in Beipiao
Beipiao
Beipiao is a city in Chaoyang prefecture, Liaoning province, in Northeast China. It has a population of 202,807. The main industry in the area is coal mining. With vertical shafts of almost 1000m, these are some of the deepest coal mines in China. The coal produced is used for coking...
, Liaoning Province, 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...
.
Description
The type and only known specimen comprised part of the maxillaMaxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
with some teeth, nearly complete fore and hind legs; and ten partial tail vertebrae. It is estimated to have been about 90 centimetres (3 ft) long in life. Graciliraptor is extremely lightly built for a non-avian theropod, with very elongated middle caudal vertebrae and lower leg bones. The femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
is thirteen centimetres long and total body length was estimated at one metre. The posterior articular processes of the tail vertebrae, or postzygapophyses, are connected by a thin bone sheath or lamina, that extends to the back over an eighth of the centrum of the following vertebra, thus further stiffening the middle tail, already immobilised by the typical dromaeosaurid long prezygapophyses.
Graciliraptor has been found in the lowest portions of the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
, the Lujiatun Member, below the rocks where similar early dromaeosaurids (such as 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...
and Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...
) were found. It is, in geological age, the oldest named dromaeosaurid, and the oldest known from good fossil remains (dromaeosaurid fossils date back all the way to the Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
, but consist mostly of teeth).
Classification
As an early dromaeosaurid, Graciliraptor provided information on the early evolution and diversification of the group. It shares several characteristics in common with both early troodontidsTroodontidae
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...
and avialan birds
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
, supporting a close relationship between avialans, troodontids, and dromaeosaurids.
Xu and Wang considered Graciliraptor to have been closely related to Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...
, a similar dromaeosaurid from the slightly younger Jiufotang Formation
Jiufotang Formation
The Jiufotang Formation is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms. . It is a member of the Jehol group. The exact age of the Jiufotang has been debated for years, with...
. Later it was placed in the Microraptorinae
Microraptorinae
Microraptorinae is a subfamily of Dromaeosauridae. Microraptorines were among the most primitive dromaeosaurids. They appeared 125 million years ago in China. Many may have been semi-arboreal gliders...
.