Soumyasaurus is a small silesaurid dinosauriform from the Late Triassic (Norian) Cooper Canyon Formation of western Texas.[1]

Temporal range: Norian, ~220 Ma
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauriformes
Clade: Dracohors
Clade: Silesauridae
Genus: Soumyasaurus
Sarıgül, Agnolín & Chatterjee, 2018
Type species
Soumyasaurus aenigmaticus
Sarıgül, Agnolín & Chatterjee, 2018


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]


Soumyasaurus aenigmaticus

Lewisuchus admixtus

Pisanosaurus mertii

Silesaurus opolensis

Sacisaurus agudoensis

Eucoelophysis baldwini

Asilisaurus kongwe


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]


  1. ^ a b c d e Sarıgül, Volkan; Agnolín, Federico; Chatterjee, Sankar (2018). "Description of a multitaxic bone assemblage from the Upper Triassic Post Quarry of Texas (Dockum group), including a new small basal dinosauriform taxon" (PDF). Historia Natural. 8 (1). ISSN 1853-6581.
  2. ^ Langer, Max C.; Ferigolo, Jorge (2013-04-23). "The Late Triassic dinosauromorph Sacisaurus agudoensis (Caturrita Formation; Rio Grande do Sul, Brazil): anatomy and affinities". Geological Society, London, Special Publications. 379: SP379.16. doi:10.1144/SP379.16. ISSN 0305-8719.

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, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.


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


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.


Echinodon (pronounced eh-KY-no-don) meaning "hedgehog tooth" in reference to the spines on its teeth (Ancient Greek: εχινος, romanized: echinos, lit. 'hedgehog', + ὀδών, odṓn, 'tooth'), occasionally known as Saurechinodon, is a genus of small European dinosaur of the early Cretaceous Period (Berriasian age), 140 million years ago.

Haya griva

Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.


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


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 (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.


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


Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.


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).


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 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.


Unaysauridae is a family of basal sauropodomorphs from the Late Triassic of India and Brazil.


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.


Yueosaurus is an extinct genus of basal ornithopod dinosaur known from Zhejiang Province, China.


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