Gasosaurus

Gasosaurus (simplified Chinese: 气龙; traditional Chinese: 氣龍)[1] (/ɡˈæsəˈsɔːrəs/) 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/sauros ("lizard / generic reptile"). 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.

Gasosaurus
Temporal range: Middle Jurassic, 171.6–161.2 Ma
Gasosaurus skeletal
Skeletal restoration illustrating known material in white
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: Avetheropoda
Genus: Gasosaurus
Dong & Tang, 1985
Type species
Gasosaurus constructus
Dong & Tang, 1985

Discovery and naming

The first and to date only fossils, albeit postcranial (missing the skull), were recovered in 1985 during the construction of a gas facility, which explains the dinosaur's unusual name. It consists of laterally compressed teeth, 4 cervical, 7 dorsal, 5 sacral, and 7 caudal vertebrae, both humeri, and highly abraded and reconstructed pelvic and hind limb material that includes the left ilium, left ischium, left pubis, left femur, left tibia and left fibula.[2] The fossils were defined as the type species Gasosaurus constructus by the paleontologists Dong Zhiming and Tang Zilu.

Description

Gasosaurus constructus
Restoration
Gasosaurus constructus scale diagram
Scale diagram

Gasosaurus is a carnivorous theropod with strong legs but short arms. It measured between 3.5 to 4 metres (11 to 13 ft) in length, with a weight of around 150 kilograms (330 lb). However, some estimates put its weight as high as 400 kilograms (880 lb),[3] as very little is known about it.

Many potentially informative features of the holotype skeleton (IVPP V7264) are difficult to assess based on published descriptions and images. The taxon represents a tetanuran based on the presence of a pubic peduncle of the ilium that is substantially larger than the ischial peduncle. Examination of casts reveals that the lesser trochanter does not rise above the level of the femoral head, and instead, the proximal portion of the femoral head is broken and the lesser trochanter reaches approximately midlevel of the head as in non-coelurosaurian tetanurans.[4]

Furthermore, it is recognized by an amphiplatyan cervical centra with incipient weak ventral keel, dorsals with amphiplatyan centra, low neural arches and plate-like neural spines, dorsal neural spines lacking expanded bulks at tips, five sacral centra and arches firmly fused while neural spines not fused, presence of a humeral foramen, low ilium with a less developed anterior process, and distal ends of pubis and ischium expanded but lacking foot-like processes.[2]

Classification

Gasosaurus fossil Bishop Museum
Reconstructed skeleton with hypothetical head, Bishop Museum

Traditionally thought to be a megalosauroid,[5] Holtz (2000) found it to be a basal coelurosaurian,[6] although later Holtz et al. (2004) suggested it was a basal carnosaur (possibly a metriacanthosaurid) on the basis of data from undescribed specimens.[7] It may in fact be the most basal coelurosaurian yet known, or may even be close to the common ancestor of the two groups; in any case, it represents one of the oldest definitive tetanuran theropods. Some paleontologists have speculated that Gasosaurus and Kaijiangosaurus may be one and the same species.

Because of the fragmentary nature of the known Gasosaurus fossils, it has an uncertain position within Tetanurae, and probably lays outside Coelurosauria. A detailed restudy of the holotype is underway that may change its classification.[4]

Paleoecology

Gasosarurus lived during the mid-Jurassic period (Bathonian and/ or Callovian stages), around 164 million years ago.[8] It coexisted with other mid-range theropods such as Chuandongocoelurus and Kaijiangosaurus, two other dinosaurs found from the Lower Shaximiao Formation. These three taxa pertain to medium to large bodied theropods and are known from associated prostcranial skeletons. China, boasts the highest taxic diversity of Middle Jurassic theropods of all body sizes from anywhere in the world. Most Middle Jurassic theropods from china are 'medium-sized', as are the majority of Middle Jurassic theropods globally.[9]

These similar dinosaurs show an intriguing combination of derived tetanuran synapomorphies and primitive features shared with non-tetanurans, which suggest they occupy a basal position within Tetanurae. Understanding the anatomy of Chinese Jurassic taxa may reveal further details of primitive tetanuran anatomy and help resolve the early evolution of this successful theropod clade. Future exploration of the Chinese Middle Jurassic theropod record may bring new insights into the diversification of Tetanurae, the origin of larger body sizes among more derived theropods, and Middle Jurassic paleobiogeography.[9]

References

  1. ^ "Gasosaurus DinosaurWorld Entry". dinosaur.net.cn. February 7, 2005. Archived from the original on February 7, 2005. Retrieved November 3, 2017.
  2. ^ a b G., Peng; Ye, Y.; Gao, Y.; Shu, C.; Jiang, S. (2005). "Jurassic Dinosaur Faunas in Zigong". 彭光照 叶 勇 高玉辉 舒纯康 江 山 著.
  3. ^ "Gasosaurus Paleoserver Entry". Dinobase. University of Bristol-Department of Geology. April 30, 2001. Archived from the original on March 7, 2005. Retrieved November 3, 2017.
  4. ^ a b Carrano, M. T.; Benson, R. B. J.; S. D., Sampson (2012). "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 10 (2): 211–300. doi:10.1080/14772019.2011.630927.
  5. ^ Dong and Tang, 1985. A new Mid-Jurassic theropod (Gasosaurus constructus gen et sp. nov.) from Dashanpu, Zigong, Sichuan Province, China. Vertebrata PalAsiatica. 23(1), 77-82.[1]
  6. ^ Holtz, 2000. A new phylogeny of the carnivorous dinosaurs. Gaia. 15, 5-61.
  7. ^ Holtz TR Jr, Molnar RE, Currie PJ. 2004. Basal Tetanurae. In: Weishampel DB, Dodson P, Osmólska H, eds. The dinosauria, 2nd edn. Berkeley, CA: University of California Press, 71–110.
  8. ^ Benton, Michael J. (2012). Prehistoric Life. Edinburgh, Scotland: Dorling Kindersley. p. 260. ISBN 978-0-7566-9910-9.
  9. ^ a b Brusatte, S. L.; Benson, R. B. J.; Xu, X. (2010). "The evolution of large-bodied theropod dinosaurs during the Mesozoic in Asia". Journal of Iberian Geology. 36 (2): 275–296. doi:10.5209/JIGE.33861.
Averostra

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

Avetheropoda

Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.

Bathonian

In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian age succeeds the Bajocian age and precedes the Callovian age.

Cerapoda

Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.

Datousaurus

Datousaurus, meaning "Big-head Lizard" (from the Chinese da tou "Big Head" and Greek sauros/σαυρος "lizard") was a dinosaur from the Middle Jurassic. It was a sauropod collected from the Lower Shaximiao Formation in Dashanpu, Zigong Sichuan province, China. It shared the local Middle Jurassic landscape with other sauropods such as Shunosaurus, Omeisaurus, Protognathosaurus, the ornithopod Xiaosaurus, the early stegosaur Huayangosaurus as well as the carnivorous Gasosaurus.

Dinosauriformes

Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.

Haya griva

Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.

Hexinlusaurus

Hexinlusaurus is a genus of basal ornithischian dinosaur from the Middle Jurassic of China. The holotype (ZDM T6001, Zigong Dinosaur Museum, Dashanpu, People's Republic of China), consists of an almost complete, articulated skull and some postcranial material, collected from a terrestrial sandstone within the Lower Shaximiao Formation (?Bajocian) at the famous dinosaur-bearing quarries at Dashanpu. A paratype (ZDM T6002) consists of a partial skull and postcranial remains. Previously, it had been described as a species of Yandusaurus, Y. multidens (He and Cai, 1983), but was reclassified as a new taxon by Paul M. Barrett, Richard J. Butler and Fabien Knoll in 2005, who diagnosed this anatomically conservative species as follows: "A small ornithischian dinosaur distinguished from all other basal ornithischians by a single autapomorphy, the presence of a marked concavity that extends over the lateral surface of the postorbital." The etymology of the genus name honors Professor He Xin-Lu (from the Chengdu University of Technology) who originally named the specimen as Y. multidens + the Greek sauros (=lizard). Hexinlusaurus was a small, fleet-footed herbivore.

Other dinosaurs known from Dashanpu include the sauropod Shunosaurus, the theropod Gasosaurus, and the stegosaur Huayangosaurus.

Before being officially named Hexinlusaurus, this genus was briefly known under the informal name "Proyandusaurus". This name originally appeared in an abstract attributed to Fabien Knoll, which was apparently published without his consent.[1][2]

Huayangosaurus

Huayangosaurus is a genus of stegosaurian dinosaur from the Middle Jurassic of China. The name derives from "Huayang" (華陽), an alternate name for Sichuan (the province where it was discovered), and "saurus", meaning "lizard". It lived during the Bathonian to Callovian stages, around 165 million years ago, some 20 million years before its famous relative, Stegosaurus appeared in North America. At only 4.5 metres long, it was also much smaller than its famous cousin. Found in the Lower Shaximiao Formation, Huayangosaurus shared the local Middle Jurassic landscape with the sauropods Shunosaurus, Datousaurus, Omeisaurus and Protognathosaurus, the ornithopod Xiaosaurus and the carnivorous Gasosaurus. It was found in Huayang in China.

Jeholosauridae

Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.

Jingshanosaurus

Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.

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.

Melanorosauridae

The Melanorosauridae were a family of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Melanorosauridae was first coined by Friedrich von Huene in 1929. Huene assigned several families of dinosaurs to the infraorder "Prosauropoda": the Anchisauridae, the Plateosauridae, the Thecodontosauridae, and the Melanorosauridae. Since then, these families have undergone numerous revisions. Galton and Upchurch (2004) considered Camelotia, Lessemsaurus, and Melanorosaurus members of the family Melanorosauridae. A more recent study by Yates (2007) indicates that the melanorosaurids were instead early sauropods.

Neotheropoda

Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Orodrominae

Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.

Raeticodactylidae

Raeticodactylidae is a family of eudimorphodontoid eopterosaurian pterosaurs that lived in Switzerland during the Late Triassic. The family includes Caviramus, and the type genus Raeticodactylus, which are both known from the Kössen Formation, around 205 mya. Raeticodactylidae was first used in 2014 by Andres et al., as a group of all pterosaurs closer to Raeticodactylus than Eudimorphodon. The following phylogenetic analysis follows the topology of Andres et al. (2014).

Riojasauridae

Riojasauridae is a family of sauropod-like dinosaurs from the Upper Triassic. It is known primarily from the genera Riojasaurus and Eucnemesaurus. Sites containing Riojasauridae include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and Ischigualasto, in La Rioja Province, Argentina ( where fossils of Riojasaurus have been recovered).

Xixiposaurus

Xixiposaurus is a genus of prosauropod dinosaur which existed in what is now Lower Lufeng Formation, China during the lower Jurassic period. It was first named by Sekiya Toru in 2010 and the type species is Xixiposaurus suni.

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