Jeholosaurus
Encyclopedia
Jeholosaurus is a genus
of ornithischia
n dinosaur
from the Early Cretaceous
Period. It is thought to have been a small ornithopod presumably related to the hypsilophodont
s, and an herbivore
. Although the back teeth are like those of a plant eater, the front premaxilla
ry teeth are sharp and pointed like a carnivorous dinosaur. This may mean that Jeholosaurus was omnivorous, eating both plants and animals.
. The actual fossil
site is located in the Yixian Formation
, near Beipiao City, Liaoning Province, China
. Jeholosaurus was found in a 130 million year old sandstone and it is thought that an enormous volcanic eruption occurred burying everything within a 50-60 mile radius. The name Jeholosaurus means "lizard from Jehol
"; Jehol refers to the name of an old geographical area in western Liaoning
and northern Hebei
. The type
and only known species is Jeholosaurus shangyuanensis. The generic name honors Shangyuan where it was first discovered.
specimen of Jeholosaurus, on which the genus is based, is IVPP
V 12529. It is 71.1 centimetres (28 in) long with a 35.6 centimetres (14 in) long tail, nearly half the length of the complete dinosaur. The length of the skull is 6.3 centimetres (2.5 in) and the mandible
s are 5.9 centimetres (2.3 in) each. The front legs are 25.4 centimetres (10 in) long and the back legs are 33 centimetres (13 in). The femur
is 9 centimetres (3.5 in) long and the tibia
is 10.7 centimetres (4.2 in).
Jeholosaurus. The premaxilla has six teeth and the maxilla
has at least thirteen teeth. The deeply inset ventral margin in the maxilla suggests cheeks may have been present. The nasals have large foramina
dorsolaterally and a midline fossa. No palpebrae
are preserved. The specimens have cervical vertebrae
and caudal vertebrae. The femur is bowed and has an anterior trochanter
slightly lower than the greater trochanter
and a third as wide as the latter. They are separated by a shallow cleft and the extensor groove is absent. The fourth trochantor is pendent. The foot has four metatarsals and the longest is metatarsal III with a length of 5.5 centimetres (2.2 in) and it is placed more anteriorly than the other metatarsals. Metatarsal I is more posterior and metatarsal I is reduced to a splint. Jeholosaurus had enlarged laterodorsal nasal foramina
; quadratojugal
fenestra more than 25% maximum quadratojugal
length; quadratojugal less than 30% of skull height; predentary
almost 150% of premaxillary body length; dentary extends posteriorly almost to posterior border of angular.
.
Jeholosaurus is not fully classified and more studies have to be done, but for the present time it was placed into the Hypsilophodontidae family for the following reasons:
was based on analysis by Makovicky et al., 2011.
The following cladogram was based on analysis by Zheng and colleagues in 2009.
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 ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
n 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 thought to have been a small ornithopod presumably related to the hypsilophodont
Hypsilophodont
Hypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 1–2 meters long . They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age...
s, and an 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...
. Although the back teeth are like those of a plant eater, the front premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
ry teeth are sharp and pointed like a carnivorous dinosaur. This may mean that Jeholosaurus was omnivorous, eating both plants and animals.
History and discovery
The first Jeholosaurus specimens were described in 20002000 in paleontology
-Newly named insects:-Newly named placoderms:-Amphibians:-Ichthyosaurs:-Newly named crurotarsans:-Newly named dinosaurs:Data courtesy of George Olshevsky's dinosaur genera list and Dr...
. The actual fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
site is located in 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...
, near Beipiao City, 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...
. Jeholosaurus was found in a 130 million year old sandstone and it is thought that an enormous volcanic eruption occurred burying everything within a 50-60 mile radius. The name Jeholosaurus means "lizard from Jehol
Jehol
Jehol could mean either a province or a city:* Jehol Province, former province in northeastern China* Chengde, the capital of above provinceNamed after the province:* Jehol Biota* Jeholodens* Jeholopterus* Jeholornis* Jeholosaurus...
"; Jehol refers to the name of an old geographical area in 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"...
and northern Hebei
Hebei
' is a province of the People's Republic of China in the North China region. Its one-character abbreviation is "" , named after Ji Province, a Han Dynasty province that included what is now southern Hebei...
. The type
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...
and only known species is Jeholosaurus shangyuanensis. The generic name honors Shangyuan where it was first discovered.
Size
The typeHolotype
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 of Jeholosaurus, on which the genus is based, is IVPP
Institute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...
V 12529. It is 71.1 centimetres (28 in) long with a 35.6 centimetres (14 in) long tail, nearly half the length of the complete dinosaur. The length of the skull is 6.3 centimetres (2.5 in) and the mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
s are 5.9 centimetres (2.3 in) each. The front legs are 25.4 centimetres (10 in) long and the back legs are 33 centimetres (13 in). 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 9 centimetres (3.5 in) long and the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
is 10.7 centimetres (4.2 in).
Anatomy
Most of the specimens had incomplete skulls and had to be restored. Some of the specimens have extremely large orbits compared to the skull size. The snout is short which means those specimens are probably those of juvenileJuvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
Jeholosaurus. The premaxilla has six teeth and the maxilla
Maxilla
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...
has at least thirteen teeth. The deeply inset ventral margin in the maxilla suggests cheeks may have been present. The nasals have large foramina
Nasal foramina
-External links:* http://zemlin.shs.uiuc.edu/Skull/slide-Pages/27.htm...
dorsolaterally and a midline fossa. No palpebrae
Palpebral (bone)
The palpebral bone is a small dermal bone found in the region of the eye socket in a variety of animals, including crocodilians and ornithischian dinosaurs. In ornithischians, it can form a prong that projects from the front upper corner of the orbit...
are preserved. The specimens have cervical vertebrae
Cervical vertebrae
In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...
and caudal vertebrae. The femur is bowed and has an anterior trochanter
Trochanter
In human anatomy, the trochanter is a part of the thigh bone. It can refer to:* Greater trochanter* Lesser trochanter* Third trochanter-See also:* Intertrochanteric crest* Intertrochanteric line...
slightly lower than the greater trochanter
Trochanter
In human anatomy, the trochanter is a part of the thigh bone. It can refer to:* Greater trochanter* Lesser trochanter* Third trochanter-See also:* Intertrochanteric crest* Intertrochanteric line...
and a third as wide as the latter. They are separated by a shallow cleft and the extensor groove is absent. The fourth trochantor is pendent. The foot has four metatarsals and the longest is metatarsal III with a length of 5.5 centimetres (2.2 in) and it is placed more anteriorly than the other metatarsals. Metatarsal I is more posterior and metatarsal I is reduced to a splint. Jeholosaurus had enlarged laterodorsal nasal foramina
Nasal foramina
-External links:* http://zemlin.shs.uiuc.edu/Skull/slide-Pages/27.htm...
; quadratojugal
Quadratojugal
The quadratojugal is a small jaw bone that is present in most amphibians, reptiles, and birds, but has been lost in mammals. It is connected to the jugal as well as other bones, though these may vary with species....
fenestra more than 25% maximum quadratojugal
Quadratojugal
The quadratojugal is a small jaw bone that is present in most amphibians, reptiles, and birds, but has been lost in mammals. It is connected to the jugal as well as other bones, though these may vary with species....
length; quadratojugal less than 30% of skull height; predentary
Predentary
The predentary is an 'extra' bone in the front of the lower jaw, which extended the dentary . It is found in the fossilised remains of ornithischian dinosaurs, which were herbivorous. The predentary coincided with the premaxilla in the upper jaw. Together they formed a beak-like apparatus used to...
almost 150% of premaxillary body length; dentary extends posteriorly almost to posterior border of angular.
Classification
The Jeholosaurus pubis bone points downward and toward the tail (backwards), parallel with the ischium, with a forward-pointing process to support the abdomen. This makes a four-pronged pelvic structure similar to the ornithischian hip bone. This description placed Jeholosaurus under the order OrnithischiaOrnithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
.
Jeholosaurus is not fully classified and more studies have to be done, but for the present time it was placed into the Hypsilophodontidae family for the following reasons:
- The premaxilla of Jeholosaurus had fairly elongated and deeply concave subnarial process which is seen in hypsilophodonts.
- There are six teeth extend along the premaxilla which is the same number as LesothosaurusLesothosaurusLesothosaurus is an herbivorous ornithischian dinosaur. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus is monotypic, having only one valid species, Lesothosaurus diagnosticus, within the genus....
had, but these teeth are slender and recurved without denticles, as in the hypsilophodonts ZephyrosaurusZephyrosaurusZephyrosaurus is a genus of hypsilophodont ornithopod dinosaur. It is based on a partial skull and postcranial fragments discovered in the Aptian-Albian-age Lower Cretaceous Cloverly Formation of Carbon County, Montana...
and ThescelosaurusThescelosaurusThescelosaurus was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous-Tertiary extinction event around 65.5 million years ago...
. - The maxillaMaxillaThe 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...
has an antorbital fossa about 14% of the cranial length and a small antorbital fenestra located posteriorly, and this is similar to the condition in hypsilophodonts. - The posterior jugal process expands distally, similar to YandusaurusYandusaurusYandusaurus is a genus of herbivorous basal euornithopod dinosaur from the Bathonian age of China.-Discovery and naming:...
. - The postorbital and frontal are typical of basal hypsilophodonts.
- A round fenestra penetrates the bone, as in hypsilophodonts.
Phylogeny
The following cladogramCladogram
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...
was based on analysis by Makovicky et al., 2011.
The following cladogram was based on analysis by Zheng and colleagues in 2009.