| Soumyasaurus Temporal range: Late Triassic, ~ | |
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Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauriformes |
| Clade: | Dracohors |
| 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]
| Silesauridae |
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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. Much controversy remains over the animal, and there are many different interpretations of what Protoavis 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 of basal saurischian dinosaur from the Late Triassic, living in India. It was a small bipedal omnivore.
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.
Lagerpeton is a genus of lagerpetid avemetatarsalian, comprising a single species, L. chanarensis. First described from the Chañares Formation of Argentina by A. S. Romer in 1971, Lagerpeton's anatomy is somewhat incompletely known, with fossil specimens accounting for the pelvic girdle, hindlimbs, posterior presacral, sacral and anterior caudal vertebrae. Skull and shoulder material has also been described.
Lewisuchus is a genus of archosaur that lived during the Middle Triassic (Ladinian). As a silesaurid dinosauriform, it was a member of the group of reptiles 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.
Teleocrater 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.
Dinosauromorpha is a clade of avemetatarsalian archosaurs 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.
Paleorhinus is an extinct genus of basal phytosaur known from the Late Triassic of Texas and Wyoming, United States, Bavaria, Germany and possibly Poland. It contains two valid species, the type species: Paleorhinus bransoni and Paleorhinus angustifrons. Paleorhinus had a length of about 2.5 meters.
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.
Morturneria is an extinct genus of plesiosaur from the Late Cretaceous of what is now Antarctica.
The Tecovas Formation is a geological formation in Texas.
Machaeroprosopus is an extinct genus of pseudopalatine phytosaurid from the Late Triassic of the southwestern United States. M. validus, once thought to be the type species of Machaeroprosopus, was named in 1916 on the basis of three complete skulls from Chinle Formation, Arizona. The skulls have been lost since the 1950s, and a line drawing in the original 1916 description is the only visual record of the specimen. Another species, M. andersoni, was named in 1922 from New Mexico, and the species M. adamanensis, M. gregorii, M. lithodendrorum, M. tenuis, and M. zunii were named in 1930. Most species have been reassigned to the genera Smilosuchus, Rutiodon, Pseudopalatus, or Phytosaurus. Until recently, M. validus was considered to be the only species that has not been reassigned. Thus, Machaeroprosopus was considered to be a nomen dubium or "doubtful name" because of the lack of diagnostic specimens that can support its distinction from other phytosaur genera. However, a taxonomic revision of Machaeroprosopus, conducted by Parker et al., revealed that UW 3807, the holotype of M. validus, is not the holotype of Machaeroprosopus, while the previously named species Pseudopalatus buceros has priority as the type species of the genus. Therefore, the name Pseudopalatus must be considered a junior synonym of Machaeroprosopus, and all species of the former must be reassigned to the later. This revised taxonomy was already accepted in several studies, including Stocker and Butler (2013). Stocker and Butler (2013) also treated M. andersoni as a valid species, and not a junior synonym of Machaeroprosopus buceros as was previously suggested by Long and Murry (1995).
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Lutungutali 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.
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.
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