Asilisaurus

Asilisaurus (/ɑːˌsiːliːˈsɔːrəs/ ah-SEE-lee-SOR-əs; from Swahili, asili ("ancestor" or "foundation"), and Greek, σαυρος (sauros, "lizard") is an extinct genus of silesaurid archosaur. It is one of the oldest known animals on the dinosaur/pterosaur side of the archosaurian tree (the Avemetatarsalia), dating to about 245 million years ago.[1]

Asilisaurus
Restoration in a quadrupedal stance

Fossils were uncovered in Tanzania and date back to the Anisian stage of the Middle Triassic. It was described in 2010 by a team of researchers from the United States, Germany, and South Africa, in the journal Nature; the type species is A. kongwe. It is the first example of an avian-line radiation during the Anisian, with the diversification of archosaurs during this time previously only documented from crocodylian-line archosaurs.[1] It was the first non-dinosaurian dinosauriform recovered from Africa.[2]

Asilisaurus measured from 1 to 3 metres (3 to 10 ft) long and 0.5 to 1 metre (2 to 3 ft) high at the hip, and weighed 10 to 30 kilograms (20 to 70 lb).[2]

Femora assigned to Asilisaurus exhibit both slender and robust morphologies. Among other avian-line archosaurs, this variation has traditionally been interpreted as sexual dimorphism. A 2016 analysis of the growth trajectories of Asilisaurus, based on hundreds of long bones assigned to the genus, found that the development of muscle scars exhibited multiple polymorphic trajectories; this suggests that the exhibited variation among Asilisaurus and other avian-line archosaurs is better characterized as having been caused by individual variation rather than sex-dependent differences.[3]

Asilisaurus
Temporal range: Middle Triassic, 245 Ma
Asilisaurus kongwe
Reconstructed skeleton in a bipedal stance
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dracohors
Clade: Silesauridae
Genus: Asilisaurus
Nesbitt et al., 2010
Species:
A. kongwe
Binomial name
Asilisaurus kongwe
Nesbitt et al., 2010

References

  1. ^ a b Nesbitt, S.J.; Sidor, C.A.; Irmis, R.B.; Angielczyk, K.D.; Smith, R.M.H.; Tsuji, L.A. (2010). "Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira". Nature. 464 (7285): 95–98. doi:10.1038/nature08718. PMID 20203608.
  2. ^ a b "Oldest known dinosaur relative discovered". ScienceDaily. March 3, 2010. Retrieved March 3, 2010.
  3. ^ Griffin, C. T.; Nesbitt, Sterling J. (2016-03-04). "The femoral ontogeny and long bone histology of the Middle Triassic (?late Anisian) dinosauriform Asilisaurus kongwe and implications for the growth of early dinosaurs". Journal of Vertebrate Paleontology. 36 (3): e1111224. doi:10.1080/02724634.2016.1111224. ISSN 0272-4634.
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.

Aphanosauria

Aphanosauria ("hidden lizards") is group of reptiles distantly related to dinosaurs (including birds). They were at the base of a group known as Avemetatarsalia, one of two main branches of archosaurs. The other main branch, Pseudosuchia, includes modern crocodilians. Aphanosaurs possessed features from both groups, indicating that they are the oldest and most primitive known clade of avemetatarsalians, at least in terms of their position on the archosaur family tree. Other avemetatarsalians include the flying pterosaurs, small bipedal lagerpetids, herbivorous silesaurids, and the incredibly diverse dinosaurs, which survive to the present day in the form of birds. Aphanosauria is formally defined as the most inclusive clade containing Teleocrater rhadinus and Yarasuchus deccanensis but not Passer domesticus (House sparrow) or Crocodylus niloticus (Nile crocodile). This group was first recognized during the description of Teleocrater. Although only known by a few genera, Aphanosaurs had a widespread distribution across Pangaea in the Middle Triassic.They were fairly slow quadrupedal long-necked carnivores, a biology more similar to basal archosaurs than to advanced avemetatarsalians such as pterosaurs, lagerpetids, and early dinosaurs. In addition, they seemingly possess 'crocodile-normal' ankles (with a crurotarsal joint), showing that 'advanced mesotarsal' ankles (the form acquired by many dinosaurs, pterosaurs, lagerpetids, and advanced silesaurids) were not basal to the whole clade of Avemetatarsalia. Nevertheless, they possessed elevated growth rates compared to their contemporaries, indicating that they grew quickly, more like birds than modern reptiles. Despite superficially resembling lizards, the closest modern relatives of aphanosaurs are birds.

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.

Jingshanosaurus

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

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).

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.

Nyasasaurus

Nyasasaurus (meaning "Lake Nyasa lizard") is an extinct genus of dinosauriform reptile from the Middle Triassic Manda Formation of Tanzania that appears to be the earliest known dinosaur. The type species Nyasasaurus parringtoni was first described in 1956 in the doctoral thesis of English paleontologist Alan J. Charig, but it was not formally described until 2013. Previously, the oldest record of dinosaurs was from Argentina and dated back to the late Carnian stage, about 231.4 million years ago. Nyasasaurus comes from a deposit that dates back to the Anisian stage, meaning that it predates other early dinosaurs by about 12 million years.

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.

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.

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.

Teleocrater

Teleocrater (meaning "completed basin", in reference to its closed acetabulum) is a genus of avemetatarsalian archosaur from the Middle Triassic Manda Formation of Tanzania. The name was coined by English paleontologist Alan Charig in his 1956 doctoral dissertation, but was only formally published in 2017 by Sterling Nesbitt and colleagues. The genus contains the type and only species T. rhadinus. Uncertainty over the affinities of Teleocrater have persisted since Charig's initial publication; they were not resolved until Nesbitt et al. performed a phylogenetic analysis. They found that Teleocrater is most closely related to the similarly enigmatic Yarasuchus, Dongusuchus, and Spondylosoma in a group that was named the Aphanosauria. Aphanosauria was found to be the sister group of the Ornithodira, the group containing dinosaurs and pterosaurs.

A carnivorous quadruped measuring 7–10 feet (2.1–3.0 m) long, Teleocrater is notable for its unusually long neck vertebrae. The neural canals in its neck vertebrae gradually become taller towards the back of the neck, which may be a distinguishing trait. Unlike the Lagerpetidae or Ornithodira, the hindlimbs of Teleocrater are not adapted for running; the metatarsal bones are not particularly elongated. Also unlike lagerpetids and ornithodirans, Teleocrater inherited the more flexible ankle configuration present ancestrally among archosaurs, suggesting that the same configuration was also ancestral to Avemetatarsalia but was lost independently by several lineages. Histology of the long bones of Teleocrater indicates that it had moderately fast growth rates, closer to ornithodirans than crocodilians and other pseudosuchians.

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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