Sarcosaurus

Sarcosaurus (meaning "flesh lizard") is a genus of theropod dinosaur, roughly 3.5 metres (11 ft) long. It lived during the Sinemurian stage of the Early Jurassic, about 194 million years ago. Sarcosaurus is one of the earliest known Jurassic theropods, and one of only a handful of theropod genera from this time period.

Sarcosaurus
Temporal range: Early Jurassic, 194 Ma
Sarcosaurus known material
Skeletal reconstruction showing known material of the holotype (bottom) and referred specimen ("Liassaurus")
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Superfamily: Coelophysoidea
Genus: Sarcosaurus
Andrews, 1921
Type species
Sarcosaurus woodi
Andrews, 1921
Synonyms

Description

Sarcosaurus woodi
Pelvis and parts of femur and dorsal vertebra

Fossils of Sarcosaurus were found in the Lower Lias of England. The type species, Sarcosaurus woodi, was first described by Charles William Andrews in 1921 shortly after a partial skeleton had been found by S.L. Wood near Barrow-on-Soar. The generic name is derived from Greek sarx, "flesh". The specific name honours Wood. The holotype, BMNH 4840/1, consists of a pelvis, a vertebra and the upper part of a femur. The preserved length of the femur is 31.5 centimetres (12.4 in).[1]

A second species, Sarcosaurus andrewsi, was named by Friedrich von Huene in 1932,[2] based on a 445 millimetres (17.5 in) tibia, BMNH R3542, described by Arthur Smith Woodward in 1908 and found near Wilmcote.[3] Confusingly von Huene in the same publication named the very same fossil Magnosaurus woodwardi. Later he made a choice for S. andrewsi to be the valid name.[4] In 1974 S. andrewsi was reclassified as Megalosaurus andrewsi by Michael Waldman, on the probably erroneous assumption it was a megalosaurid.[5] A later study concluded the two species to be indistinguishable except for size,[6] but other authors consider any identity to be unprovable as there are no comparable remains and conclude both species to lack autapomorphies and therefore to be nomina dubia.[7]

Von Huene in 1932 referred a partial skeleton from the collection of the Warwick Museum to S. woodi but the identity is unproven; in 1995 it was given the generic name "Liassaurus"[8] but this has remained a nomen nudum. The specimen is likely one individual, located in the same stratiagraphic position as the holotypic specimen. Unfortunately, there are few available overlapping elements from the specimen and the Holotype. Both specimens preserve a relatively complete femur: however, the features of both (an anteromedially directed head, a relatively long fourth trochanter and a trochanteric shelf) are plesiomorphic and thus do not indicate conspecifity or clade membership. It is noted, however, that there are no features which are present in one specimen but not the other. Andrews originally assigned Sarcosaurus to the Megalosauridae. The first to suggest a more basal position was Samuel Paul Welles who placed it in the Coelophysidae.[9] Later analyses resulted in either a position in the Ceratosauria,[10] or in the Coelophysoidea.[11] Ezcurra (2012) found Sarcosaurus to be the most basal ceratosaur in a large unpublished analysis.[12]. In 2018, Andrea Cau in the large analysis of Saltriovenator found Sarcosaurus to be a Dilophosaur, in a very strong position[13]

See also

References

  1. ^ Andrews, C.W., 1921, "On some remains of a theropodous dinosaur from the Lower Lias of Barrow-on-Soar", Annals and Magazine of Natural History, series 9 8: 570-576 [1]
  2. ^ von Huene, F., 1932, Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte, Monographien zur Geologie und Palaeontologie 1(4) pp. 361
  3. ^ Woodward, A.S. 1908. "Note on a megalosaurian tibia from the Lower Lias of Wilmcote, Warwickshire". Annals and Magazine of Natural History. 8(1): 257-259
  4. ^ Huene, F. von, 1956, Paläontologie und Phylogenie der niederen Tetrapoden. Gustav Fischer Verlag, Jena. 716 pp
  5. ^ Waldman, M. 1974. "Megalosaurids from the Bajocian (Middle Jurassic) of Dorset". Paleontology 17(2): 325-339
  6. ^ Carrano and Sampson (2004). "A review of coelophysoids (Dinosauria: Theropoda) from the Early Jurassic of Europe, with comments on the late history of the Coelophysoidea." N. Jb. Geol. Palaont. Mh., 2004(9): 537-558.
  7. ^ D. Naish and D. M. Martill. 2007. "Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia". Journal of the Geological Society, London 164: 493-510
  8. ^ Pickering, S. 1995. Jurassic Park: Unauthorized Jewish Fractals in Philopatry. A Fractal Scaling in Dinosaurology Project, 2nd revised printing. Capitola, California. 478 pp
  9. ^ S.P. Welles. 1984. "Dilophosaurus wetherilli (Dinosauria, Theropoda): osteology and comparisons". Palaeontographica Abteilung A 185: 85-180
  10. ^ J A. Gauthier. 1986. "Saurischian monophyly and the origin of birds". In: The Origin of Birds and the Evolution of Flight, K. Padian (ed.), Memoirs of the California Academy of Sciences 8: 1-55
  11. ^ M.T. Carrano, J.R. Hutchinson, and S.D. Sampson. 2005. "New information on Segisaurus halli, a small theropod dinosaur from the Early Jurassic of Arizona". Journal of Vertebrate Paleontology 25 (4): 835-849
  12. ^ Ezcurra, 2012. Phylogenetic analysis of Late Triassic - Early Jurassic neotheropod dinosaurs: Implications for the early theropod radiation. Journal of Vertebrate Paleontology. Program and Abstracts 2012, 91.
  13. ^ Dal Sasso C, Maganuco S, Cau A. 2018. The oldest ceratosaurian (Dinosauria: Theropoda), from the Lower Jurassic of Italy, sheds light on the evolution of the three-fingered hand of birds. PeerJ 6:e5976

External links

1921 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 1921.

Anchisauria

The Anchisauria were a clade of sauropodomorph dinosaurs that lived during the Late Triassic and Early Jurassic. The name Anchisauria was first used by Galton and Upchurch in the second edition of The Dinosauria. Galton and Upchurch assigned two families of dinosaurs to the Anchisauria: the Anchisauridae and the Melanorosauridae. The more common prosauropods Plateosaurus and Massospondylus were placed in the sister clade Plateosauria.

However, recent research indicates that Anchisaurus is closer to sauropods than traditional prosauropods; thus, Anchisauria would also include Sauropoda.The following cladogram simplified after an analysis presented by Blair McPhee and colleagues in 2014.

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.

Blue Lias

The Blue Lias is a geologic formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassic times, between 195 and 200 million years ago. The Blue Lias is famous for its fossils, especially ammonites.

Its age corresponds to the Rhaetian to lower Sinemurian stages of the geologic timescale, thus fully including the Hettangian stage. It is the lowest of the three divisions of the Lower Jurassic period and, as such, is also given the name Lower Lias. Stratigraphically it can be subdivided into three members: the Wilmcote Limestone, Saltford Shale and Rugby Limestone.

Cerapoda

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

Coelophysoidea

Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the coelurosaurs, with which they were formerly classified, and some species had delicate cranial crests. Sizes range from about 1 to 6 m in length. It is unknown what kind of external covering coelophysoids had, and various artists have portrayed them as either scaly or feathered. Some species may have lived in packs, as inferred from sites where numerous individuals have been found together.

Examples of coelophysoids include Coelophysis, Procompsognathus and Liliensternus. Most dinosaurs formerly referred to as being in the dubious taxon "Podokesauridae" are now classified as coelophysoids.

Dilophosauridae

Dilophosauridae is a family of medium to large sized theropod dinosaurs. The name Dilophosauridae is derived from Greek, with “di” meaning “two,” “lophos” meaning “crest,” “sauros” meaning “lizard,” and “idae” meaning “family”. While the name suggests that all dilophosaurids have two crests, this is not applicable to all dilophosaurids. The Dilophosauridae is anchored by the genus Dilophosaurus, and therefore the name comes from the distinctive two crests of the genus.

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.

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.

Magnosaurus

Magnosaurus (meaning 'large lizard') was a genus of basal tetanuran theropod dinosaur from the Middle Jurassic of England. It is based on fragmentary remains and has often been confused with or included in Megalosaurus.

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.

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).

Sinemurian

In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic epoch or series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian.In Europe the Sinemurian age, together with the Hettangian age, saw the deposition of the lower Lias, in Great Britain known as the Blue Lias.

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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