''Siamraptor'' is an extinct genus of

carcharodontosauria Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Metriacanthosauridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae. Allosauroids, alongside the family Megalosauroidea, were among t ...

n dinosaur, containing the single species ''S. suwati'', known from the Khok Kruat Formation of

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is bo ...

. It is the first definitive named carcharodontosaurian species known from

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...

Discovery

Siamraptor reconstruction 2019 (Mario Lanzas)

Between 2007 and 2009, the Japan-Thailand Dinosaur Project carried out excavations at the village of Saphan Hin, subdistrict Suranaree,

Mueang Nakhon Ratchasima District Mueang Nakhon Ratchasima ( th, เมืองนครราชสีมา, ) is one of 32 districts of Nakhon Ratchasima province, northeastern Thailand. Overview Nakhon Ratchasima was built in the reign of King Narai the Great of Ayutthay ...

, in Nakhon Ratchasima Province. The finds included bones from a theropod new to science. In 2019, the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

''Siamraptor suwati'' was named and described by Duangsuda Chokchaloemwon, Soki Hattori, Elena Cuesta, Pratueng Jintasakul, Masateru Shibata and Yoichi Azuma. The generic name is derived from "Siam", the former name of Thailand, and the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

word ''raptor'' ("robber"). The specific name honours

Suwat Liptapanlop Suwat Liptapanlop ( th, สุวัจน์ ลิปตพัลลภ, , ; born 9 February 1955 in Ratchaburi Province) is a Thai entrepreneur, politician and sports official based in Nakhon Ratchasima. He has held different cabinet posts in ...

, who supported the Northeastern Research Institute of Petrified Wood and Mineral Resources. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, NRRU-F01020008, was found in a layer of the Khok Kruat Formation dating from the

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

. It consists of a rear right lower jaw including the surangular, prearticular and articular. Further material referred to ''S. suwati'' includes the isolated remains of at least three individuals, mostly consisting of skull and lower jaw fragments as well as a manual ungual, a series of three cervical vertebrae, two partial ischia, a caudal vertebra, two dorsal vertebral centra and a neural spine, a partial tibia and a left pedal phalanx.

Description

The body length of ''Siamraptor'' has been estimated at . The describing authors indicated some distinguishing traits. These are

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

, unique derived characters, relative to the

Allosauroidea Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four family (biology), families — the Metriacanthosauridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae. Allosauroids, alongside the family Megalosauroid ...

. The

jugal bone The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...

has a lower edge that is straight instead of convex or undulating while the front branch is high, even under the eye socket. The surangular bone has a deep oval excavation to the rear of its bone shelf and four rear surangular foramina, while other theropods possess at most two. A long narrow groove runs along the suture between the surangular and the prearticular bone. The notch in the suture between the articular and prearticular is pierced by a foramen. The front neck vertebrae possess an additional pneumatic foramen excavating the parapophysis, the lower rib contact. The neck vertebrae and rear back vertebrae have paired small foramina in the base of the

neural spine The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

References

{{Taxonbar, from=Q70326252 Carcharodontosauria Aptian life Early Cretaceous dinosaurs of Asia Cretaceous Thailand Fossils of Thailand Fossil taxa described in 2019