Xuanhanosaurus | |
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An artist's restoration of Xuanhanosaurus qilixiaensis | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Genus: | † Xuanhanosaurus Dong, 1984 |
Species: | †X. qilixiaensis |
Binomial name | |
†Xuanhanosaurus qilixiaensis Dong, 1984 | |
Xuanhanosaurus (meaning "Xuanhan lizard") is a genus of theropod dinosaur that lived during the Middle Jurassic (Bathonian) of the Sichuan Basin, China, around 166.0 million years ago. [2] This Taxon represents one of the various Carnosaurian taxa found on the Middle Jurassic of the region, uncovered on the Lower Shaximiao Formation. [3] Although it has been known for more than 40 years, this taxon has been the subject of very few studies, although most seem to agree that it is a Tetanuran, possibly a basal Allosauroid, highlighting the fact that it has a vestigial fourth metacarpal.
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 specimen was recovered in 1979, when the author was conducting a Dinosaurian Fossil survey in Sichuan Province, when was guided by Liu Yawen and the 137th team to examine the Qilixia section, where they recovered the holotype of this new taxon at the southern flank of the Qili Dorsal Slope. [3] The holotype specimen, IVPP V.6729, was found in China's Lower Shaximiao Formation. It consists of a partial skeleton without a skull, namely a scapula missing the posterior end, coracoid, a possible sternum humerus, radius, ulna, manus, as well a few fragmentary dorsal vertebrae. [3]
Xuanhanosaurus, originally thought to be around 6 m long, was approximately 4.5 meters (15 ft) in length, with a weight of 250 kilograms (550 lb). [5] 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. [3] 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. [6] The retention of the 4th metarcarpal is the most notorious feature of this taxon, yet the presence of a convex proximal surface on the distal carpal 2 has been used to arge it represents a second stage in the evolution of the "semilunate" carpal. [7] Some recent work have notified that beyond the 4th metarcarpal, Xuanhanosaurus also retains ceratosaurian-like short phalanges II-1, similar in length to the ones recovered on Saltriovenator . [8] The scapula was found to be bulkier than in Allosaurus . The distal humerus is enlarged laterally, forming a one-inch step. [3] The vertebrae are posteriorly concave and anteriorly protruding, with cervical centra having flat anterior articular surfaces, also seen in Condorraptor , Piatnitzkysaurus and "Szechuanosaurus" zigongensis, yet lacking posterior pneumatic foramen or fossa, which is seen on the first 2 genera. [9]
Originally, Xuanhanosaurus was assigned by Dong to the Megalosauridae, when this group was meant to include a larger amount of taxa, and was argued to be in the middle stage of the evolution of the Tetanureae due to it´s vestigial 4th metacarpals. [3] Latter it was found by Roger Benson in 2009 to belong to a primitive lineage of the Megalosauroidea. [10] A more recent study by Benson and colleagues in 2010 found that it was more likely to be the most primitive known member of the Metriacanthosauridae family. [4] In 2018, based on several conditions such as the length and retention of the vestigial 4th metacarpal, it was argued that this taxon and "Szechuanosaurus" zigongensis belong to early-diverging branches of the ceratosaurian-tetanuran node. [8] In 2019, Rauhut and Pol recovered Xuanhanosaurus outside of Metriacanthosauridae, as the basalmost member of Allosauroidea. [6]
Carnosauria |
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Tetanurae is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, compsognathids and maniraptorans. Tetanurans are defined as all theropods more closely related to modern birds than to Ceratosaurus and contain the majority of predatory dinosaur diversity. Tetanurae likely diverged from its sister group, Ceratosauria, during the late Triassic. Tetanurae first appeared in the fossil record by the Early Jurassic about 190 mya and by the Middle Jurassic had become globally distributed.
Gasosaurus is a genus of tetanuran theropod that lived approximately 171.6 to 161.2 million years ago during the middle of the Jurassic Period. The name "Gasosaurus" is derived from the English "gasoline" and the Greek σαῦρος. Only one species is currently recognised, G. constructus, from which the specific name honours the gasoline company that found the Dashanpu fossil quarry in Sichuan Province, China, now named as the Lower Shaximiao Formation.
Yangchuanosaurus is an extinct genus of metriacanthosaurid theropod dinosaur that lived in China from the Middle Jurassic to Early Cretaceous periods, and was similar in size and appearance to its North American and European relative, Allosaurus. Yangchuanosaurus hails from the Upper Shaximiao Formation and Suining Formation and was the largest predator in a landscape that included the sauropods Mamenchisaurus and Omeisaurus and the stegosaurs Chialingosaurus, Tuojiangosaurus and Chungkingosaurus. This theropod was named after the area in which was discovered, Yongchuan, in China.
Allosauridae is a family of medium to large bipedal, carnivorous allosauroid theropod dinosaurs from the Late Jurassic. Allosauridae is a fairly old taxonomic group, having been first named by the American paleontologist Othniel Charles Marsh in 1878. Allosaurids are characterized by an astragalus with a restriction of the ascending process to the lateral part of the bone, a larger medial than lateral condyle, and a horizontal groove across the face of the condyles.
Megalosauridae is a monophyletic family of carnivorous theropod dinosaurs within the group Megalosauroidea. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dinosaurs. They were a relatively primitive group of basal tetanurans containing two main subfamilies, Megalosaurinae and Afrovenatorinae, along with the basal genus Eustreptospondylus, an unresolved taxon which differs from both subfamilies.
Megaraptor is a genus of large theropod dinosaur that lived in the ages of the Late Cretaceous. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America. Initially thought to have been a giant dromaeosaur-like coelurosaur, it was classified as a neovenatorid allosauroid in previous phylogenies, but more recent phylogeny and discoveries of related megaraptoran genera has placed it as either a basal tyrannosauroid or a basal coelurosaur with some studies still considering it a neovenatorid.
Monolophosaurus is an extinct genus of tetanuran theropod dinosaur from the Middle Jurassic Shishugou Formation in what is now Xinjiang, China. It was named for the single crest on top of its skull. Monolophosaurus was a mid-sized theropod at about 5–5.5 metres (16–18 ft) long and weighed 475 kilograms (1,047 lb).
Megalosauroidea is a superfamily 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. They are possibly paraphyletic in nature with respect to Allosauroidea.
Chuandongocoelurus is a genus of carnivorous tetanuran theropod dinosaur from the Jurassic of China.
Condorraptor is an extinct genus of megalosauroid theropod dinosaur. Its genus name means 'robber from Cerro Condor', referencing a nearby village, while its species name, currumili, is named after Hipolito Currumil, the landowner and discoverer of the locality. It was among the earliest large South American theropods, having been found in Lower Jurassic strata of the Cañadón Asfalto Formation in the Cañadón Asfalto Basin of Argentina. The type species, described in 2005, is Condorraptor currumili. It is based on a tibia, with an associated partial skeleton that may belong to the same individual. Initially described as a basal tetanuran, Benson (2010) found it to be a piatnitzkysaurid megalosauroid and the sister taxon of Piatnitzkysaurus, a finding supported by later studies.
Metriacanthosauridae is an extinct family of allosauroid 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. The records of the group are mostly confined to Asia, though Metriacanthosaurus is known from Europe. Metriacanthosauridae is used as a senior synonym of Sinraptoridae.
Kaijiangosaurus 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.
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. The most famous and best understood allosauroid is the North American genus Allosaurus.
Lourinhanosaurus was a genus of carnivorous theropod dinosaur that lived during the Late Jurassic Period (Kimmeridgian/Tithonian) in Portugal. It is one of many large predators discovered at the Lourinhã Formation and probably competed with coeval Torvosaurus gurneyi, Allosaurus europaeus, and Ceratosaurus.
Avetheropoda, or "bird theropods", is a clade that includes Carnosaurs and coelurosaurs to the exclusion of other Dinosaurs.
The Shaximiao Formation is a Middle to Late Jurassic aged geological formation in Sichuan, China, most notable for the wealth of dinosaurs fossils that have been excavated from its strata. The Shaximiao Formation is exposed in and around the small township of Dashanpu, situated seven kilometres north-east from Sichuan's third largest city, Zigong, in the Da'an District.
Megaraptora is a clade of carnivorous tetanuran theropod dinosaurs with controversial relations to other theropods. Its derived members, the Megaraptoridae are noted for their large hand claws and robust forelimbs, which are usually reduced in size in other large theropods.
Piatnitzkysauridae is an extinct family of megalosauroid or basal allosauroid dinosaurs. It only consists of three to four known dinosaur genera: Condorraptor, Marshosaurus, Piatnitzkysaurus and possibly Xuanhanosaurus. The most complete and well known member of this family is Piatnitzkysaurus, which also gives the family its name.
Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.
The Xintiangou Formation is a geological formation in China. Part of the stratigraphy of the Sichuan Basin, it is of an uncertain Middle Jurassic age, with preliminary U-Pb estimates giving an age range of 170 ma. It predominantly consists of interbedded mudstone and sandstone, with subordinate shelly limestone. At the Laojun site remains of lungfish, bony fish, freshwater sharks, temnospondyls, plesiosaurs, crocodyliformes, the Xinjiangchelyid turtle Protoxinjiangchelys and tritylodontids are known. The dinosaurs Sanxiasaurus,Yunyangosaurus, and indeterminate sauropods are also known from the formation. Theropod and ornithopod tracks have also been reported from the formation.