| Soumyasaurus Temporal range: Late Triassic, | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | † Ornithischia (?) |
| Family: | † Silesauridae |
| Genus: | † Soumyasaurus Sarıgül, Agnolín & Chatterjee, 2018 |
| Type species | |
| †Soumyasaurus aenigmaticus Sarıgül, Agnolín & Chatterjee, 2018 | |
Soumyasaurus is a small silesaurid dinosauriform from the Late Triassic (Norian) Cooper Canyon Formation of western Texas. [1]
Soumyasaurus is named in honor of Sankar Chatterjee's oldest son, Soumya (likewise, the shuvosaurid pseudosuchian Shuvosaurus was named for another of Chatterjee's sons, Shuvo). The specific epithet aenigmaticus derives from the Latin word aenigma, meaning "enigma or riddle", referring to the poor preservation of the fossil. [1]
The only known element of Soumyasaurus is a small (less than 3 cm long), poorly preserved left dentary, missing its anterior end and containing some teeth with an estimated tooth count of at least 15. Soumyasaurus is mostly characterised by its teeth, which are fused to the jaw bone by a rim fibrous bone at their bases (ankylothecodont), a characteristic trait of silesaurids.
Unlike the typically leaf-shaped teeth of other silesaurids, the teeth of Soumyasaurus are smooth and conical, resembling those of Asilisaurus, and are readily distinguishable from the uniquely triangular, possibly tricuspid teeth of the contemporary silesaurid Technosaurus .
Unfortunately, it is unknown if Soumyasaurus had small serrations like Asilisaurus, as these portions of the teeth are either missing or badly damaged, and is only distinguished from it by the lower position of the Meckelian groove on the inside of the jaw. The tip of the jaw, known to be toothless and possibly supporting a beak in other silesaurids, [2] is missing and so its shape is unknown for Soumyasaurus.
Soumyasaurus was described as "minute" by Sarıgül and colleagues, inferring a small body size from the length of the preserved dentary, certainly smaller in size than the contemporary Technosaurus. [1]
A phylogenetic analysis was performed which recovered Soumyasaurus as a silesaurid, however its relationships amongst Silesauridae were unresolved. The coeval Technosaurus was not included in this analysis, as including the two taxa together unusually resulted with the archosauriform Euparkeria as the sister taxon to a polytomy containing the two dinosauriforms. [1]
The Soumyasaurus holotype was found in association with other specimens in an assemblage catalogued under TTU P-11254, including a specimen of Vancleavea (TTU P-11254a), indeterminate archosauromorph remains (TTU P-11254c-e), and remains indeterminate beyond Sauria (TTU P-11254f-i). This is similar to another assemblage at the Post Quarry where the holotype premaxilla and dentary of Technosaurus was discovered with posterior jaw bones now known to be from Shuvosaurus . It is apparent that the remains labelled TTU P-11254 were brought together in association by similar taphonomic agents, which are inconsistent with previous suggestions of a rapid flooding event. [1]
Protoavis is a problematic taxon known from fragmentary remains from Late Triassic Norian stage deposits near Post, Texas. The animal's true classification has been the subject of much controversy, and there are many different interpretations of what the taxon actually is. When it was first described, the fossils were described as being from a primitive bird which, if the identification is valid, would push back avian origins some 60-75 million years.
Postosuchus, meaning "Crocodile from Post", is an extinct genus of rauisuchid reptiles comprising two species, P. kirkpatricki and P. alisonae, that lived in what is now North America during the Late Triassic. Postosuchus is a member of the clade Pseudosuchia, the lineage of archosaurs that includes modern crocodilians. Its name refers to Post Quarry, a place in Texas where many fossils of the type species, P. kirkpatricki, were found. It was one of the apex predators of its area during the Triassic, larger than the small dinosaur predators of its time. It was a hunter which probably preyed on large bulky herbivores like dicynodonts and many other creatures smaller than itself.
Alwalkeria is a genus partly based on basal saurischian dinosaur remains from the Late Triassic, living in India.
Shuvosaurus is a genus of beaked, bipedal poposauroid pseudosuchian from the Late Triassic of western Texas. Despite superficially resembling a theropod dinosaur, especially the ostrich-like ornithomimids, it is instead more closely related to living crocodilians than to dinosaurs. Shuvosaurus is known by the type and only species S. inexpectatus, and is closely related to the very similar Effigia within the clade Shuvosauridae. Shuvosaurus was originally described from a restored skull and very few fragmentary postcranial bones as a probable ornithomimosaur, or at least a very ornithomimosaur-like early theropod. The true pseudosuchian affinities of Shuvosaurus were only recognised after the discovery of Effigia linked the skull of Shuvosaurus with similar poposauroid skeletal remains found in the same quarry.
Venaticosuchus is a genus of pseudosuchian archosaurs from the family Ornithosuchidae. Known from a single species, Venaticosuchus rusconii, this genus is described based on an incomplete skull and jaw collected from the Late Triassic (Carnian) Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina, which was deposited around 230 million years ago. This fossil material has been termed the holotype specimen PVL 2578. Venaticosuchus incorporated a myriad of features present in the other two genera of ornithosuchids, Ornithosuchus and Riojasuchus. However, it also had several unique traits, relating to the lower jaw.
Technosaurus is an extinct genus of Late Triassic silesaurid dinosauriform, from the Late Triassic Cooper Canyon Formation of Texas, United States.
Lewisuchus is a genus of archosaur that lived during the Late Triassic. As a silesaurid dinosauriform, it was a member of the group of reptiles most commonly considered to be the closest relatives of 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.
Dinosauromorpha is a clade of avemetatarsalians that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids, with later formulations specifically excluding pterosaurs from the group. Birds are the only dinosauromorphs which survive to the present day.
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 among the dozens of fossil material unearthed, 35 right femora were collected whereas only 1 left femur was found.
Prozostrodon is an extinct genus of probainognathian cynodonts that was closely related to mammals. The remains were found in Brazil and are dated to the Carnian age of the Late Triassic. The holotype has an estimated skull length of 6.7 centimetres (2.6 in), indicating that the whole animal may have been the size of a cat. The teeth were typical of advanced cynodonts, and the animal was probably a carnivore hunting reptiles and other small prey.
Morturneria is an extinct genus of plesiosaur from the Late Cretaceous of what is now Antarctica.
The Tecovas Formation is a geological formation in the Texas panhandle and eastern New Mexico. It is one of several formations encompassed by the Late Triassic Dockum Group.
The Cooper Canyon Formation is a geological formation of Norian age in Texas. It is one of several formations encompassed by the Dockum Group.
Asilisaurus ; from Swahili, asili, and Greek, σαυρος is an extinct genus of silesaurid archosaur. The type species is Asilisaurus kongwe. Asilisaurus fossils were uncovered in the Manda Beds of Tanzania and date back to the early Carnian, making it one of the oldest known members of the Avemetatarsalia. It was the first non-dinosaurian dinosauriform recovered from Africa. The discovery of Asilisaurus has provided evidence for a rapid diversification of avemetatarsalians during the Middle Triassic, with the diversification of archosaurs during this time previously only documented in pseudosuchians.
Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids comprised an early diverging clade or a paraphyletic grade within ornithischian dinosaurs. Silesaurids have a consistent general body plan, with a fairly long neck and legs and possibly quadrupedal habits, but most silesaurids are heavily fragmentary nonetheless. Furthermore, they occupied a variety of ecological niches, with early silesaurids being carnivorous and later taxa having adaptations for specialized herbivory. As indicated by the contents of referred coprolites, Silesaurus may have been insectivorous, feeding selectively on small beetles and other arthropods.
Diodorus is a genus of silesaurid dinosauromorph that lived during the Late Triassic in what is now Morocco. Fossils were discovered in the Timezgadiouine Formation of the Argana Basin, and were used to name the new genus and species Diodorus scytobrachion. The genus name honors the mythological king Diodorus and the ancient historian Diodorus Siculus; the specific name is ancient Greek for 'leathery arm' and also honors the mythographer Dionysius Scytobrachion. The holotype specimen is a partial dentary bone (front of the lower jaw), and assigned specimens include isolated teeth, two humeri (upper arm bones), a metatarsal (foot bone), and femur (thigh bone).
Libognathus is an extinct genus of procolophonid parareptile from the Late Triassic of Texas. The type and only species, Libognathus sheddi, was named in 1997 from the Cooper Canyon Formation in the fossil-rich Post Quarry, which is found in Garza County. Libognathus was the first definite procolophonid discovered in the southwestern United States, although another possible procolophonid called Chinleogomphius was reported from the southwest before Libognathus was named.
Kwanasaurus is an extinct genus of silesaurid dinosauromorph reptiles from the Late Triassic of Colorado. It is known from a single species, Kwanasaurus williamparkeri. Kwanasaurus had a deeper, stronger skull and greater specialization for herbivory compared to other silesaurids. It also possessed many unique characteristics of the snout, ilium, and lower part of the femur. It was described along with new specimens of Dromomeron from the Eagle Basin, the northernmost extent of the Chinle Formation.
Bonacynodon is an extinct genus of cynodonts that lived in what is now southern Brazil during the Triassic period. The genus is monotypic, containing only the type species Bonacynodon schultzi. B. schultzi is known from two specimens, consisting of two partial skulls and some badly preserved parts of the postcranium. Both specimens were recovered from the Pinheiros-Chiniquá Sequence, part of the Santa Maria Supersequence of the Paraná Basin. This sequence preserves a faunal association known as the Dinodontosaurus Assemblage Zone, which contains numerous other species of cynodonts, dicynodonts and reptiles. Bonacynodon was a small, likely insectivorous cynodont, whose length has been estimated at around 30 centimetres (12 in). It can be distinguished from other cynodonts by its large, serrated (saw-like) canine teeth. Together with the genus Probainognathus of Argentina, it made up the family Probainognathidae, one of the earliest-diverging lineages of the clade Probainognathia. It was a fairly close relative of mammals, the only group of cynodonts alive today.
Vetusodon is an extinct genus of cynodonts belonging to the clade Epicynodontia. It contains one species, Vetusodon elikhulu, which is known from four specimens found in the Late Permian Daptocephalus Assemblage Zone of South Africa. With a skull length of about 18 centimetres (7.1 in), Vetusodon is the largest known cynodont from the Permian. Through convergent evolution, it possessed several unusual features reminiscent of the contemporary therocephalian Moschorhinus, including broad, robust jaws, large incisors and canines, and small, single-cusped postcanine teeth.
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