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.[1]

Silesauridae
Temporal range: Middle TriassicLate Triassic, 245–203 Ma
Silesaurus1
Life restoration of Silesaurus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dracohors
Clade: Silesauridae
Langer et al., 2010
Genera

Classification

Silesauridae is the sister group to Dinosauria. The group was named in 2010 by paleontologist Max C. Langer et al. They defined it as a branch-based clade of all archosaurs closer to Silesaurus opolensis than to either Heterodontosaurus tucki or Marasuchus lilloensis. At the same time, a second group of scientists independently named Silesauridae as a node-based clade consisting of Lewisuchus, Silesaurus, their last common ancestor and all their descendants.[2] Currently, both definitions encompass the same group of animals. In a later paper, Sterling J. Nesbitt et al. (2010) noted that the earlier definition by Langer et al. did not include a diagnosis, and so was not sufficient to create a ranked family-level name according to the ICZN. Therefore, the family Silesauridae is attributed to Nesbitt et al. (2010) while the clade Silesauridae is attributed to Langer et al. (2010).[3]

The fossils range in age from the Anisian to the Norian stages of the Triassic, about 245 to 203 million years ago.[2][4] The cladogram below follows the phylogenetic analysis of basal ornithodirans conducted by Christian Kammerer, Sterling Nesbitt and Neil Shubin (2012).[3]

Ornithodira 

Pterosauria

 Dinosauromorpha 
 Lagerpetonidae 

Lagerpeton chanarensis

Dromomeron gregorii

Dromomeron romeri

 Dinosauriformes 

Marasuchus lilloensis

Dracohors

Dinosauria

 Silesauridae 

Lewisuchus/Pseudolagosuchus

Asilisaurus kongwe

Eucoelophysis baldwini

Silesaurus opolensis

Sacisaurus agudoensis

Diodorus scytobrachion

A large phylogenetic analysis of early dinosaurs and dinosauromorphs carried out by Matthew Baron, David Norman and Paul Barrett (2017) and published in the journal Nature recovered Silesauridae as a monophyletic sister group to Dinosauria. The study also recovered the taxon Agnosphitys within the clade Silesauridae, close to Lewisuchus and its synonymous taxon Pseudolagosuchus.[5]

References

  1. ^ Martin Qvarnström; Joel Vikberg Wernström; Rafał Piechowski; Mateusz Tałanda; Per E. Ahlberg; Grzegorz Niedźwiedzki (2019). "Beetle-bearing coprolites possibly reveal the diet of a Late Triassic dinosauriform". Royal Society Open Science. 6 (3): Article ID 181042. doi:10.1098/rsos.181042. PMC 6458417. PMID 31031991.
  2. ^ a b Nesbitt, Sterling J., Sidor, Christian A., Irmis, Randall B., Angielczyk, Kenneth D., Smith, Roger M.H. and Tsuji, Linda A. (2010) "Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira." Nature 464(7285):95-8 Supplement
  3. ^ a b Kammerer, C. F.; Nesbitt, S. J.; Shubin, N. H. (2012). "The First Silesaurid Dinosauriform from the Late Triassic of Morocco". Acta Palaeontologica Polonica. 57 (2): 277. doi:10.4202/app.2011.0015.
  4. ^ Langer, M.C., Ezcurra, M.D., Bittencourt, J.S., and Novas, F.E. (2010). "The origin and early evolution of dinosaurs". Biological Reviews 85:55-110. doi:10.1111/j.1469-185X.2009.00094.x
  5. ^ 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

External links

Agnosphitys

Agnosphitys (; "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.

Avemetatarsalia

Avemetatarsalia (meaning "bird metatarsals") is a clade name established by British palaeontologist Michael Benton in 1999 for all crown group archosaurs that are closer to birds than to crocodilians. An alternate name is Pan-Aves, or "all birds", in reference to its definition containing all animals, living or extinct, which are more closely related to birds than to crocodilians. Almost all avemetatarsalians are members of a similarly defined subgroup, Ornithodira. Ornithodira is defined as the last common ancestor of dinosaurs and pterosaurs, and all of its descendants.Members of this group include the Dinosauromorpha, Pterosauromorpha, the genus Scleromochlus, and Aphanosauria. Dinosauromorpha contains more basal forms, including Lagerpeton and Marasuchus, as well as more derived forms, including dinosaurs. Birds belong to the dinosaurs as members of the theropods. Pterosauromorpha contains Pterosauria, which were the first vertebrates capable of true flight. Aphanosauria is a Triassic group of gracile carnivorous quadrupeds which was recognized in 2017.

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.

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.

Dinosauromorpha

Dinosauromorpha is a clade of archosaurs that includes the clade Dinosauria (dinosaurs), and all animals more closely related to dinosaurs than to pterosaurs. Birds are the only surviving dinosauromorphs.

Diodorus scytobrachion

Diodorus is a genus of silesaurid dinosauriforms (relatives of basal dinosaurs) from the Late Triassic (Carnian - Norian) Timezgadiouine Formation of the Argana Basin of Morocco. It is named after Diodorus, a legendary king of the Berber people and son of Sufax, the founder of Tangier and also in honour of Diodorus Siculus, a 1st-century Greek historian who wrote about North Africa. The specific epithet, scytobrachion, is ancient Greek for "leather armed", but also honors Dionysius Scytobrachion, a mythographer who chronicled the mythical history of North Africa. The holotype and all referred remains were found in a single quarry at the base of the Irohalene Mudstone Member of the Timezgadiouine Formation in the northeastern Argana Basin, 2.9 kilometres (1.8 mi) east of Imziln, Morocco.

Diodorus can be distinguished from other silesaurids by the presence of forward-slanted teeth that decrease in size towards the front end of the dentary (lower jaw) and a distinct side ridge running parallel to the dentary tooth socket margin. In a phylogenetic analysis, Diodorus was found to be the sister taxon to the Brazilian silesaurid Sacisaurus.

Eodromaeus

Eodromaeus (meaning "dawn runner") was a genus of basal theropod dinosaur known from the Late Triassic (Carnian) Valle de la Luna Member of the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. It has been cited by Sereno as resembling a supposed common ancestor to all dinosaurs, the "Eve" of the dinosaurs.

Eucoelophysis

Eucoelophysis (meaning "true hollow form") is a genus of dinosauriform from the Late Triassic (Norian) period Chinle Formation of New Mexico. It was assumed to be a coelophysid upon description, but a study by Nesbitt et al. found that it was actually a close relative of Silesaurus, which was independently supported by Ezcurra (2006), who found it to be the sister group to Dinosauria, and Silesaurus as the next most basal taxon.However, the relationships of Silesaurus are uncertain. Dzik found it to be a dinosauriform (the group of archosaurs from which the dinosaurs evolved), but did not rule out the possibility that it represents a primitive ornithischian.

Ignotosaurus

Ignotosaurus is an extinct genus of silesaurid dinosauriform known from the Late Triassic (Carnian) Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina. It was therefore contemporary with early dinosaurs such as Herrerasaurus, and lived in the same place.

Lewisuchus

Lewisuchus is a genus of archosaur that lived during the Middle Triassic (Ladinian); it was a silesaurid dinosauriform, a member of the group of reptiles which led to the dinosaurs. Lewisuchus was about 1 metre (3.3 ft) long. Fossils have been found in the Chañares Formation of Argentina. It exhibited osteoderms along its back.

Lutungutali

Lutungutali (meaning "high hip" in the Bemba language) is an extinct genus of silesaurid dinosauriform from the Middle Triassic of Zambia. The single type species of the genus is Lutungutali sitwensis. Lutungutali was named in 2013 and described from a fossil specimen, holotype NHCC LB32, including hip bones and tail vertebrae. The specimen was collected in 2009 from the upper Ntawere Formation, which dates to the Anisian stage of the Middle Triassic. Lutungutali is the first known silesaurid from Zambia and, along with the Tanzanian silesaurid Asilisaurus and dinosauriform Nyasasaurus, the oldest bird-line archosaur known from body fossils (i.e. parts of the skeleton).

Orionides

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

Sacisaurus

Sacisaurus is a silesaurid dinosauriform from the Late Triassic (Norian) Caturrita Formation of southern Brazil. The scientific name, Sacisaurus agudoensis, refers to the city where the species was found, Agudo in the Rio Grande do Sul state, whereas Sacisaurus refers to Saci, a famous one-legged creature from Brazilian mythology, because the fossil skeleton was found with a leg missing.

Saltopus

Saltopus ("hopping foot") is a genus of very small bipedal dinosauriform containing the single species S. elginensis from the late Triassic period of Scotland. It is one of the most famous Elgin Reptiles.

Silesaurus

Silesaurus is a genus of silesaurid dinosauriform from the Late Triassic, approximately 230 million years ago in the Carnian faunal stage of what is now Poland.

Fossilized remains of Silesaurus have been found in the Keuper Claystone in Krasiejów near Opole, Silesia, Poland, which is also the origin of its name. The type species, Silesaurus opolensis, was described by Jerzy Dzik in 2003. It is known from some 20 skeletons, making it one of the best-represented of the early dinosauriformes.

Soumyasaurus

Soumyasaurus is a small silesaurid dinosauriform from the Late Triassic (Norian) Cooper Canyon Formation of western Texas.

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