''Graciliraptor'' (meaning "graceful thief") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

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 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 ...

Period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

. It is a microraptorine dromaeosaurid. 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 specime ...

''Graciliraptor lujiatunensis'' was first named and described in 2004 by Xu Xing and Wang Xiaoling. The generic name is derived from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''gracilis'' and ''raptor''. The specific name refers to the village Lujiatun where the fossil site is located. Its

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 ...

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 sever ...

IVPP V 13474, was found in Beipiao, Liaoning Province, China.

Description

The type and only known specimen comprised part of the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

with some teeth, nearly complete fore and hind legs; and ten partial tail vertebrae. It is estimated to have been about long in life.Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2010 Appendix.
/ref> In 2010,

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 higher estimations of one metre and 1.5 kilogrammes. ''Graciliraptor'' is extremely lightly built for a non-avian theropod, with very elongated middle caudal vertebrae and lower leg bones. 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 wit ...

is thirteen centimetres long and total body length was estimated at one metre. The posterior articular processes of the tail vertebrae, or

postzygapophyses The articular processes or zygapophyses ( Greek ζυγον = " yoke" (because it links two vertebrae) + απο = "away" + φυσις = " process") of a vertebra are projections of the vertebra that serve the purpose of fitting with an adjacent vert ...

, 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.Xu, X. and Wang, X.-L. (2004). "A New Dromaeosaur (Dinosauria: Theropoda) from the Early Cretaceous Yixian Formation of Western Liaoning." ''Vertebrata PalAsiatica'', 42(2): 11-119. ''Graciliraptor'' has been found in the lowest portions 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 exq ...

, the Lujiatun Member, below the rocks where similar early dromaeosaurids (such as ''

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. ...

'' and ''

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 ...

'') 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).

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

troodontids Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discov ...

and avialan birds, supporting a close relationship between avialans, troodontids, and dromaeosaurids. Xu and Wang considered ''Graciliraptor'' to have been closely related to ''

'', a similar dromaeosaurid from the slightly younger

Jiufotang Formation The Jiufotang Formation ( Chinese: 九佛堂组, pinyin: ''jiǔfótáng zǔ'') is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms (see ...

. Later it was placed in the

Microraptorinae Microraptoria (Greek, μίκρος, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a clade of basal dromaeosaurid theropod dinosaurs. The first microraptorians appeared 125 million years ago in China. Many are known for long feather ...

.F. Knoll and J. I. Ruiz-Omeñaca. 2009. "Theropod teeth from the basalmost Cretaceous of Anoual (Morocco) and their palaeobiogeographical significance". ''Geological Magazine'' 146(4): 602-616

References

External links

A New Dromaeosaur (Dinosauria: Theropoda) from the Early Cretaceous Yixian Formation of Western Liaoning.
{{Taxonbar, from=Q134623 Microraptorians Taxa named by Xu Xing Early Cretaceous dinosaurs of Asia Yixian fauna

Description

Classification

See also

References

External links