Yixianosaurus
Encyclopedia
Yixianosaurus is a maniraptora
n theropod dinosaur
genus
from the Early Cretaceous
of China
.
The type species
, Yixianosaurus longimanus, was formally named and described by Xu Xing and Wang Xiaolin in 2003. Its partial skeleton was discovered in 2001, in Liaoning
at Wangjiagou in northeastern China. The generic name refers to the Yixian Formation
. The specific name means "with a long hand" from Latin
longus, "long", and manus, "hand".
Yixianosaurus is known only from a single specimen, holotype
IVPP V12638, which likely derived from the Dawangzhangzi Bed (early Aptian
stage, 122 million years ago). It is a compression fossil
, preserved on a single slab, that however has been sawed into several pieces. It consists of the shoulder girdle together with a pair of fossilized arms complete with fossilized feathers and some ribs and gastralia. Yixianosaurus has a very long hand, 140% of the length of the 89 millimetres (3.5 in) long humerus
. The second finger is the longest. The fingers bear large and recurved claws. The feathers are not preserved well enough to show a specific structure, but they appear similar to the contour feathers of some Yixian Formation bird
s. The large hands could have served in catching prey or assisted climbing. The total body length has been estimated at one metre, the weight at one kilogram.
The describers considered the exact placement of Yixianosaurus within Maniraptora
to be uncertain
, but because the hand length resembled that of another feathered dinosaur, Epidendrosaurus (now Scansoriopteryx
), they suggested it was a close relative of the Scansoriopterygidae
.
Maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea...
n 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...
genus
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...
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...
of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
.
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...
, Yixianosaurus longimanus, was formally named and described by Xu Xing and Wang Xiaolin in 2003. Its partial skeleton was discovered in 2001, in 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"...
at Wangjiagou in northeastern China. The generic name refers to 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 specific name means "with a long hand" 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...
longus, "long", and manus, "hand".
Yixianosaurus is known only from a single specimen, 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 V12638, which likely derived from the Dawangzhangzi Bed (early Aptian
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 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
stage, 122 million years ago). It is a compression fossil
Compression fossil
A compression fossil is a fossil preserved in sedimentary rock that has undergone physical compression. While it is uncommon to find animals preserved as good compression fossils, it is very common to find plants preserved this way...
, preserved on a single slab, that however has been sawed into several pieces. It consists of the shoulder girdle together with a pair of fossilized arms complete with fossilized feathers and some ribs and gastralia. Yixianosaurus has a very long hand, 140% of the length of the 89 millimetres (3.5 in) long humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
. The second finger is the longest. The fingers bear large and recurved claws. The feathers are not preserved well enough to show a specific structure, but they appear similar to the contour feathers of some Yixian Formation bird
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...
s. The large hands could have served in catching prey or assisted climbing. The total body length has been estimated at one metre, the weight at one kilogram.
The describers considered the exact placement of Yixianosaurus within Maniraptora
Maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea...
to be uncertain
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
, but because the hand length resembled that of another feathered dinosaur, Epidendrosaurus (now Scansoriopteryx
Scansoriopteryx
Scansoriopteryx is a genus of avialan dinosaur. Described from only a single juvenile fossil specimen found in Liaoning, China, Scansoriopteryx is a sparrow-sized animal that shows adaptations in the foot indicating an arboreal lifestyle. It possessed an unusual, elongated third finger...
), they suggested it was a close relative of the Scansoriopterygidae
Scansoriopterygidae
Scansoriopterygidae is a family of maniraptoran dinosaurs, known from three well-preserved fossils unearthed in the Daohugou fossil beds of Liaoning, China....
.