Xiaotingia
Encyclopedia
Xiaotingia is a genus
of bird-like
theropod dinosaur
from early Late Jurassic
deposits of western Liaoning
, China
, containing a single species, Xiaotingia zhengi.
STM 27-2, an articulated and nearly complete skeleton
including the skull
. It was probably collected in the Linglongta area, Jianchang, from the Tiaojishan Formation
.
and the type species
is Xiaotingia zhengi. Generic name and specific name together honour Zheng Xiaoting.
with Archaeopteryx
, Dromaeosauridae
and Troodontidae
to the exclusion of other groups traditionally seen as birds. Xu et al. therefore (re)defined the concepts of Deinonychosauria
and Avialae
to the extent that Archaeopteryx and Xiaotingia belonged to the Deinonychosauria and Archaeopteryx no longer was an avialan. This led to popular reports that "Archaeopteryx is no longer a bird", though Xu et al. noted that there are several competing definitions of the clade Aves currently in use, pointing out that their definitions are compatible with a traditional Aves with Archaeopteryx as a specifier. However, this was challenged by a more thorough analysis published several months later, in which Archaeopteryx was again recovered as an avialan, while Xiaotingia remained closely allied to Anchiornis within the Troodontidae.
Cladogram
after Xu et al., 2011:
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 bird-like
Paraves
Paraves is a branch-based clade containing birds and other closely related dinosaurs. The paravians include the Avialae, including Archaeopteryx and modern birds, and the Deinonychosauria, which includes the dromaeosaurids and troodontids....
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 early Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
deposits of western 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"...
, 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...
, containing a single species, Xiaotingia zhengi.
Discovery
Xiaotingia is known from the holotypeHolotype
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...
STM 27-2, an articulated and nearly complete skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
including the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
. It was probably collected in the Linglongta area, Jianchang, from the Tiaojishan Formation
Tiaojishan Formation
The Tiaojishan Formation is a geological formation in Hebei and Liaoning, People's Republic of China, dating to the middle-late Jurassic period . It is known for its fossil plants, and is made up mainly of pyroclastic rock interspersed with basic volcanic and sedimentary rocks...
.
Etymology
Xiaotingia was first named by Xu Xing, You Hailu, Du Kai and Han Fenglu in 20112011 in paleontology
-Lobopods:-Arachnids:-Insects:-Newly named jawless vertebrates:-Newly named acanthodian:-Newly named cartilaginous fishes:-Newly named bony fishes:-Newly named lepospondyls:-Newly named temnospondyls:-Newly named lissamphibians:...
and 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...
is Xiaotingia zhengi. Generic name and specific name together honour Zheng Xiaoting.
Phylogeny
An initial cladistic analysis by Xu et al. showed that Xiaotingia formed a cladeClade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
with Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
, Dromaeosauridae
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'...
and Troodontidae
Troodontidae
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...
to the exclusion of other groups traditionally seen as birds. Xu et al. therefore (re)defined the concepts of Deinonychosauria
Deinonychosauria
The Deinonychosauria were a clade of coelurosaurian theropod dinosaurs from the Late Jurassic and Cretaceous periods. These omnivores and carnivores are known for their switchblade-like second toe claws and for displaying numerous bird-like characteristics. The clade has been divided into two...
and Avialae
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
to the extent that Archaeopteryx and Xiaotingia belonged to the Deinonychosauria and Archaeopteryx no longer was an avialan. This led to popular reports that "Archaeopteryx is no longer a bird", though Xu et al. noted that there are several competing definitions of the clade Aves currently in use, pointing out that their definitions are compatible with a traditional Aves with Archaeopteryx as a specifier. However, this was challenged by a more thorough analysis published several months later, in which Archaeopteryx was again recovered as an avialan, while Xiaotingia remained closely allied to Anchiornis within the Troodontidae.
Cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
after Xu et al., 2011: