Alxasaurus
Encyclopedia
Alxasaurus is a genus
of therizinosaur
oid alxasaurid theropod dinosaur
from the Early Cretaceous
Period of Inner Mongolia
. It is one of the earliest known members of the superfamily
Therizinosauroidea, but it already possessed the body shape - including the long neck, short tail, and long hand claws - of later therizinosauroids. Like other members of this group, it was a biped
al herbivore
with a large gut to process plant material. Several specimens are known and the largest was a little over 12 feet (3.8 m) long.
This dinosaur was first described and named by Canadian
paleontologist Dale Russell
and his Chinese colleague, Dong Zhiming
, in a paper published in 1993. However, although the paper is technically included in the last issue of the 1993 volume of the Canadian Journal of Earth Sciences
, this issue was actually released in the early weeks of 1994.
Alxasaurus is named after the Alxa Desert of Inner Mongolia, also known as the "Alashan" desert
, and the name also includes the Greek
word sauros ("lizard"). Alxa
(or Alashan) is also the name of the league, or administrative division, of the Inner Mongolia (Nei Mongol Zizhiqu) region of the People's Republic of China
. The single known species
(A. elesitaiensis) is named after Elesitai, a village found in this region, near which the fossil
remains of Alxasaurus were located.
Five Alxasaurus skeletons were recovered from the Bayin-Gobi Formation
of Inner Mongolia, which dates to the Albian
stage of the Early Cretaceous Period, or about 112 to 100 million years ago. The holotype
, specimen IVPP 88402a, which is considered to exemplify the genus and species, is the largest and most complete of the five, consisting of the mandible
(lower jaw) and some teeth, as well as many limb bones, ribs, and vertebrae, including all five sacral
(hip) vertebrae and the first nineteen tail vertebrae. The other four specimens are the paratype
s: IVPP 88301, IVPP 88402b, IVPP 88501 and IVPP 88510. Together the skeletons represent most of the bones in the body aside from the skull
.
While exhibiting many typical therizinosaur features in overall body shape and in the teeth, the skeleton of Alxasaurus also shows several features present in more typical theropods, and the discovery of this animal provided significant evidence that therizinosaurs were aberrant theropods. Specifically, the semilunate carpal bone of the wrist is found only in maniraptora
n theropods, which also include oviraptorosaurs
, dromaeosaurs
, troodontids, and bird
s. Even more basal
therizinosaurs such as Falcarius
and the feather
ed Beipiaosaurus
have since been discovered with more theropod features and have helped to solidify this arrangement. Alxasaurus is now thought to occupy a position between the early Beipiaosaurus
and later therizinosaurs such as Erlikosaurus
, Segnosaurus
, and Therizinosaurus
itself (Clark et al., 2004).
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 therizinosaur
Therizinosaur
Therizinosaurs are theropod dinosaurs belonging to the clade Therizinosauria. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People's Republic of China and Western North America...
oid alxasaurid 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
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
Period of Inner Mongolia
Inner Mongolia
Inner Mongolia is an autonomous region of the People's Republic of China, located in the northern region of the country. Inner Mongolia shares an international border with the countries of Mongolia and the Russian Federation...
. It is one of the earliest known members of the superfamily
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
Therizinosauroidea, but it already possessed the body shape - including the long neck, short tail, and long hand claws - of later therizinosauroids. Like other members of this group, it was a biped
Biped
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"...
al herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
with a large gut to process plant material. Several specimens are known and the largest was a little over 12 feet (3.8 m) long.
This dinosaur was first described and named by Canadian
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
paleontologist Dale Russell
Dale Russell
Dale A. Russell is a Canadian geologist/palaeontologist, currently Research Professor at The Department of Marine Earth and Atmospheric Sciences of North Carolina State University...
and his Chinese colleague, Dong Zhiming
Dong Zhiming
Dong Zhiming , from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, is one of China's leading paleontologists. He began working at the IVPP in 1962, learning from Yang Zhongjian who was director at the time...
, in a paper published in 1993. However, although the paper is technically included in the last issue of the 1993 volume of the Canadian Journal of Earth Sciences
Canadian Journal of Earth Sciences
The Canadian Journal of Earth Sciences is a monthly journal, published since 1963 , which reports current research in the earth sciences, geochemistry, geophysics, etc...
, this issue was actually released in the early weeks of 1994.
Alxasaurus is named after the Alxa Desert of Inner Mongolia, also known as the "Alashan" desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
, and the name also includes the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
word sauros ("lizard"). Alxa
Alxa League
Alxa League is one of 12 prefecture level divisions and three extant leagues of Inner Mongolia. The league borders Mongolia to the north, Bayan Nur to the northeast, Wuhai and Ordos to the east, Ningxia to the southeast, and Gansu to the south and west. The capital is Bayan Hot in the aimag's...
(or Alashan) is also the name of the league, or administrative division, of the Inner Mongolia (Nei Mongol Zizhiqu) region of the People's Republic 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 single known species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
(A. elesitaiensis) is named after Elesitai, a village found in this region, near which the fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains of Alxasaurus were located.
Five Alxasaurus skeletons were recovered from the Bayin-Gobi Formation
Bayin-Gobi Formation
The Bayin-Gobi Formation is a geological formation in Inner Mongolia, north China, whose strata date back to the Early Cretaceous period.Dinosaur remains are among the fossils that have been recovered from the formation.-Vertebrate paleofauna:...
of Inner Mongolia, which dates to the Albian
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
stage of the Early Cretaceous Period, or about 112 to 100 million years ago. The 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...
, specimen IVPP 88402a, which is considered to exemplify the genus and species, is the largest and most complete of the five, consisting of the mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
(lower jaw) and some teeth, as well as many limb bones, ribs, and vertebrae, including all five sacral
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
(hip) vertebrae and the first nineteen tail vertebrae. The other four specimens are the paratype
Paratype
Paratype is a technical term used in the scientific naming of species and other taxa of organisms. The exact meaning of the term paratype when it is used in zoology is not the same as the meaning when it is used in botany...
s: IVPP 88301, IVPP 88402b, IVPP 88501 and IVPP 88510. Together the skeletons represent most of the bones in the body aside from 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...
.
While exhibiting many typical therizinosaur features in overall body shape and in the teeth, the skeleton of Alxasaurus also shows several features present in more typical theropods, and the discovery of this animal provided significant evidence that therizinosaurs were aberrant theropods. Specifically, the semilunate carpal bone of the wrist is found only in 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...
n theropods, which also include oviraptorosaurs
Oviraptorosauria
Oviraptorosaurs are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot - like skulls, with or without bony crests atop the head...
, dromaeosaurs
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'...
, troodontids, and 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. Even more basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
therizinosaurs such as Falcarius
Falcarius
Falcarius is a genus of therizinosaurian dinosaur found in east-central Utah, United States. Its name is derived from the word sickle , which scientists have used to describe its unwieldy clawed hands...
and the feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
ed Beipiaosaurus
Beipiaosaurus
Beipiaosaurus is a genus of therizinosauroid theropod dinosaur from the Early Cretaceous of China.The exact classification of therizinosaurs had in the past been hotly debated, since their prosauropod-like teeth and body structure indicate that they were generally herbivorous, unlike typical...
have since been discovered with more theropod features and have helped to solidify this arrangement. Alxasaurus is now thought to occupy a position between the early Beipiaosaurus
Beipiaosaurus
Beipiaosaurus is a genus of therizinosauroid theropod dinosaur from the Early Cretaceous of China.The exact classification of therizinosaurs had in the past been hotly debated, since their prosauropod-like teeth and body structure indicate that they were generally herbivorous, unlike typical...
and later therizinosaurs such as Erlikosaurus
Erlikosaurus
Erlikosaurus is a genus of herbivorous theropod dinosaur from the late Cretaceous Period, belonging to the Therizinosauridae. Its fossils, a skull and some post-cranial fragments, were found in the Bayan Shireh Formation of Mongolia, dating to around 90 million years ago.-Discovery and naming:The...
, Segnosaurus
Segnosaurus
Segnosaurus is a genus of herbivorous theropod dinosaur belonging to the Therizinosauridae from the Cretaceous of Mongolia.-Discovery and naming:...
, and Therizinosaurus
Therizinosaurus
Therizinosaurus is a genus of very large theropod dinosaur. Therizinosaurus lived in the late Cretaceous Period , and was one of the last and largest representatives of its unique group, the Therizinosauria...
itself (Clark et al., 2004).