Xuanhanosaurus

Xuanhanosaurus (meaning "Xuanhan lizard") is a genus of theropod dinosaur that lived during the Middle Jurassic of China, around 167.7 to 161.2 million years ago.[1]

Xuanhanosaurus
Temporal range: Middle Jurassic, 167.7–161.2 Ma
Xuanhanosaurus qilixiaensis
An artist's restoration of Xuanhanosaurus qilixiaensis
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Metriacanthosauridae
Genus: Xuanhanosaurus
Dong, 1984
Species:
X. qilixiaensis
Binomial name
Xuanhanosaurus qilixiaensis
Dong, 1984

Discovery

The type species Xuanhanosaurus qilixiaensis was named by Dong Zhiming in 1984. The generic name refers to Xuanhan County in Sichuan, while the specific name is derived from the town of Qilixia. The holotype specimen, IVPP V.6729, was found in China's Lower Shaximiao Formation, part of the Dashanpu Formation. It consists of a partial skeleton without a skull.[2]

Description

Xuanhanosaurus was approximately 4.5 meters (15 ft) in length, with a weight of 250 kilograms (550 lb).[3] Xuanhanosaurus had powerful forelimbs, over 65 cm long; this, along with the retention of the fourth metacarpal in the hand, led Dong to suggest that Xuanhanosaurus might have walked on all four legs. If so, it would be the only known four-legged meat-eater among dinosaurs.[2] Later paleontologists have not agreed with Dong's original assessment. They think this dinosaur walked on its hind legs as other theropods did, pronation of the lower arm being impossible. The strong arms could instead have been useful in catching prey.

Xuanhanosaurus qilixiaensis size comparison
An X. qilixiaensis specimen compared to an average human male

Phylogeny

Assigned by Dong to the Megalosauridae, Xuanhanosaurus was found by Roger Benson in 2009 to belong to a primitive lineage of the Megalosauroidea.[4] A more recent study by Benson and colleagues found that it was more likely to be the most primitive known member of the Metriacanthosauridae family.[5]

References

  1. ^ Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix.
  2. ^ a b Dong, Z. (1984). "A new theropod dinosaur from the Middle Jurassic of Sichuan Basin". Vertebrata PalAsiatica 22(3):213-218
  3. ^ Paul, G.S. (2010). The Princeton Field Guide to Dinosaurs. Princeton University Press. p. 86.
  4. ^ Benson, R. B. J. (2010). "A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods". Zoological Journal of the Linnean Society. 158 (4): 882–935. doi:10.1111/j.1096-3642.2009.00569.x.
  5. ^ Benson, R. B. J.; Carrano, M. T; Brusatte, S. L. (2010). "A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic". Naturwissenschaften. 97 (1): 71–78. Bibcode:2010NW.....97...71B. doi:10.1007/s00114-009-0614-x. PMID 19826771. Supporting Information
1984 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1984.

Agilisaurus

Agilisaurus (; 'agile lizard') is a genus of ornithischian dinosaur from the Middle Jurassic Period of what is now eastern Asia. The name is derived from the Latin "agilis" meaning 'agile' and the Greek "sauros" meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs. Its tibia (lower leg bone) 207.0 mm in length, was longer than its femur (upper leg bone) 199.0 mm in length, which indicates that it was an extremely fast bipedal runner, using its long tail for balance, although it may have walked on all fours when browsing for food. It was a small herbivore, about 2 meters (6.5 feet) in length, and like all ornithischians, it had a beak-like structure on the ends of both upper and lower jaws to help it crop plant material.

Allosauroidea

Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Metriacanthosauridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae. Allosauroids, alongside the family Megalosauroidea, were among the apex predators that were active during the Middle Jurassic to Late Cretaceous periods. Of the fourteen allosauroid taxa, five are known for specimens with relatively complete skulls; the taxa are Allosaurus, Sinraptor, Yangchuanosaurus, Carchardontosaurus, and Acrocanthosaurus. The most famous and best understood allosauroid is the North American genus Allosaurus.

The oldest-known allosauroid, Shidaisaurus jinae, appeared in the early Middle Jurassic (probably Bajocian stage) of China. The last known definitive surviving members of the group died out around 93 million years ago in Asia (Shaochilong) and South America (Mapusaurus), though the megaraptorans may belong to the group as well. Additional, but highly fragmentary, remains probably belonging to carcharodontosaurids have been found from the Late Maastrichtian (70-66 Ma ago) in Brazil. An alternative interpretation is to attribute the remains to abelisaurids, which share the distinct pattern of curved wrinkled enamel found in the Brazilian remains with the carcharodontosaurids. This similarity between abelisaurids and carcharodontosaurids means that a definitive match between the Brazilian fossil and carcharodontosaurids cannot be made.Allosauroids had long, narrow skulls, large orbits, three-fingered hands, and usually had "horns" or ornamental crests on their heads. Although allosauroids vary in size, the group maintains a similar center of mass and hip position on their bodies. Allosauroids also exhibit reptilian-style immune systems, secreting fibrin at injured sites to prevent infections from spreading through the bloodstream. This characteristic has been observed by examining injuries and infections on allosauroid bones. It is possible that allosauroids were social animals, as many remains of allosauroids have been found in close proximity to each other. Allosauroids were likely active predators, and from studying endocasts, probably best responded to odors and loud low-frequency noises.

Dashanpu Formation

The Dashanpu Formation is a Mid to Late Jurassic rock formation in China, most notable for the wealth of dinosaurs that have been excavated from the area. The Dashanpu Formation sits in and around the small township of Dashanpu (simplified Chinese: 大山铺镇; traditional Chinese: 大山鋪鎮; pinyin: Dàshānpū zhèn), situated seven kilometres north-east from Sichuan's third largest city, Zigong, in the Da'an District.

Kaijiangosaurus

Kaijiangosaurus (meaning "Kiijiang lizard") is a genus of carnivorous tetanuran theropod dinosaur from the Middle Jurassic of China. In 1984 He Xinlu named and described the type species Kaijiangosaurus lini. The generic name refers to the River (jiang) Kai. The specific name honours the paleontologist Lin Wenqiu.

List of Asian dinosaurs

This is a list of dinosaurs whose remains have been recovered from Asia excluding the Indian Subcontinent, which was part of a separate landmass for much of the Mesozoic. This list does not include dinosaurs that live or lived after the Mesozoic era such as birds.

List of dinosaur genera

This list of dinosaurs is a comprehensive listing of all genera that have ever been included in the superorder Dinosauria, excluding class Aves (birds, both living and those known only from fossils) and purely vernacular terms.

The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered dinosaurs. Many listed names have been reclassified as everything from birds to crocodilians to petrified wood. The list contains 1559 names, of which approximately 1192 are considered either valid dinosaur genera or nomina dubia.

Marshosaurus

Marshosaurus is a genus of medium-sized carnivorous theropod dinosaur, belonging to the Megalosauroidea, from the Late Jurassic Morrison Formation of Utah and possibly Colorado.

Megalosauroidea

Megalosauroidea (meaning 'great/big lizard forms') is a superfamily (or clade) of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period. The group is defined as Megalosaurus bucklandii and all taxa sharing a more recent common ancestor with it than with Allosaurus fragilis or Passer domesticus. Members of the group include Spinosaurus, Megalosaurus, and Torvosaurus.

Metriacanthosauridae

Metriacanthosauridae is an extinct family of theropod dinosaurs that lived from the Middle Jurassic to the Early Cretaceous. When broken down into its Greek roots, it means "moderately-spined lizards". The family is split into two subgroups: Metriacanthosaurinae, which includes dinosaurs closely related to Metriacanthosaurus, and another group composed of the close relatives of Yangchuanosaurus. Metriacanthosaurids are considered carnosaurs, belonging to the Allosauroidea superfamily. The group includes species of large range in body size. Of their physical traits, most notable are their neural spines. Their fossils can be found mostly in the Northern hemisphere. Metriacanthosauridae is used as a senior synonym of Sinraptoridae.

Omeisaurus

Omeisaurus (meaning "Omei lizard") is a genus of sauropod dinosaur from the Middle Jurassic Period (Bathonian-Callovian stage) of what is now China. Its name comes from Mount Emei, where it was discovered in the lower Shaximiao Formation of Sichuan Province.

Like other sauropods, Omeisaurus was herbivorous and large. It measured 20.2 metres (66 ft) long, and weighed 9.8 tonnes.

Piatnitzkysauridae

Piatnitzkysauridae is an extinct family of megalosauroid dinosaurs. It consists of three known dinosaur genera: Condorraptor, Marshosaurus, and Piatnitzkysaurus. The most complete and well known member of this family is Piatnitzkysaurus, which also gives the family its name.

Piatnitzkysaurus

Piatnitzkysaurus ( pee-ət-NYITS-kee-SOR-əs meaning "Piatnitzky's lizard") is a genus of megalosauroid theropod dinosaur that lived approximately 166 to 164 million years ago during the middle part of the Jurassic Period in what is now Argentina. Piatnitzkysaurus was a moderately large, lightly built, bipedal, ground-dwelling carnivore that could grow up to 6.6 m (21.7 ft) long.

Theropoda

Theropoda ( or , from Greek θηρίον "wild beast" and πούς, ποδός "foot") or theropods () are a dinosaur suborder that is characterized by hollow bones and three-toed limbs. They are generally classed as a group of saurischian dinosaurs, although a 2017 paper has instead placed them in the proposed clade Ornithoscelida as the closest relatives of the Ornithischia. Theropods were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores, piscivores, and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.

Basal allosauroids
Metriacanthosauridae
Allosauria
Piatnitzkysauridae
Megalosauria

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