Agnosphitys

Agnosphitys (/ˌæɡnoʊsˈfaɪtɪs/; "unknown begetter"; sometimes mistakenly called Agnostiphys or Agnosphytis is a genus of silesaurid dinosauriform that lived during the Late Triassic. It contains only one species, the type species A. cromhallensis. Its remains include an ilium, maxilla, astragalus and humerus, which date variously from the Norian and Rhaetian stages of the Late Triassic.

The type species, Agnosphitys cromhallensis, was described by Nicholas Fraser, Kevin Padian, Gordon Walkden and A. L. M Davis in early 2002. The fossils, consisting of a partial skeleton including referred material, were found in Avon, England.

Agnosphitys
Temporal range: Late Triassic, 208 Ma
Agnosphitys cromhallensis2 copia
Pre-2017 life restoration showing it as an early dinosaur
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dracohors
Clade: Silesauridae
Genus: Agnosphitys
Fraser et al., 2002
Species:
A. cromhallensis
Binomial name
Agnosphitys cromhallensis
Fraser et al., 2002

Classification

The remains of Agnosphitys defied precise classification in the original description; the describers placed it outside Dinosauria using the definition of Dinosauria outlined by Padian and May (1995) and provided (on p. 80) the following diagnosis: "Well-defined brevis fossa on the ilium; semi-perforate acetabulum; `kidney-shaped' antitrochanter; well-developed posterior portion of the iliac blade; two sacral vertebrae; subrectangular deltopectoral crest that is 33 per cent of the length of the humerus; astragalus with a distinct ascending process and a prominent depression immediately posterior to the ascending process; in dorsal aspect an acute anteromedial corner on the astragalus."[1]

Despite the paucity of known fossils, Agnosphitys has been included in two phylogenetic analyses analyzing primitive dinosaur relationships. Yates (2007) recovered the genus as a theropod, whereas Ezcurra (2010) recovered it as a member of Guaibasauridae. More recently, Agnosphitys has been considered a silesaurid based on an as-yet-unpublished description of Asilisaurus.[2]

A large phylogenetic analysis of early dinosaurs and dinosauromorphs carried out by Matthew Baron, David Norman and Paul Barrett (2017) recovered Agnosphitys as a member of the clade Silesauridae.[3]

References

  1. ^ Nicholas C. Fraser, Kevin Padian, Gordon M. Walkden and A. L. M. Davis, 2002. Basal dinosauriform remains from Britain and the diagnosis of the Dinosauria. Palaeontology. 45(1), 79-95.
  2. ^ Nesbitt, Sidor, Irmis, Stocker, Angielczyk, and Smith, 2015. THE ANATOMY OF ASILISAURUS KONGWE (DINOSAURIFORMES: SILESAURIDAE) AND CLOSELY-RELATED TAXA PROVIDES NEW INSIGHTS INTO THE ANATOMICAL AND CHRONOLOGICAL EVOLUTION OF DINOSAURIFORMS. Journal of Vertebrate Paleontology 35 (Supplement):187A-188A.
  3. ^ Baron, M.G., Norman, D.B., and Barrett, P.M. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543: 501–506. doi:10.1038/nature21700

Further reading

  • Langer, 2004. Basal Saurischia. In Weishampel, Dodson and Osmolska. The Dinosauria Second Edition. University of California Press. 861 pp.
  • Yates, 2007. Solving a dinosaurian puzzle: the identity of Aliwalia rex Galton. Historical Biology. 19(1), 93-123.
  • Ezcurra, 2010. A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: A reassessment of dinosaur origin and phylogeny. Journal of Systematic Palaeontology. 8(3), 371-425.
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.

Cerapoda

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

Chromogisaurus

Chromogisaurus is a sauropodomorph which existed in Argentina during the Late Triassic (Carnian) period. It was a herbivore about 2 metres (6 ft 7 in) in length, and was optionally quadrupedal.

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.

Guaibasauridae

Guaibasauridae is a family of basal saurischian dinosaurs, known from fossil remains of late Triassic period formations in Brazil and Argentina.

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.

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.

Norian

The Norian is a division of the Triassic geological period. It has the rank of an age (geochronology) or stage (chronostratigraphy). The Norian lasted from ~227 to 208.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.

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).

Rhaetian

See Raetians for the Alpine people of antiquity. See Raetian language for their language.The Rhaetian is, in geochronology, the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 208.5 to 201.3 million years ago. It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age of the Jurassic).In this age, Pangaea began to break up, though the Atlantic Ocean was not yet formed.

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).

Silesauridae

Silesauridae is an extinct clade of Triassic dinosauriformes consisting of the closest known relatives of dinosaurs. As indicated by coprolite contents, some silesaurids such as Silesaurus may have been insectivorous, feeding selectively on small beetles and other arthropods.

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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