''Ratchasimasaurus'' (meaning "

Nakhon Ratchasima Nakhon Ratchasima ( th, นครราชสีมา, ) is one of the four major cities of Isan, Thailand, known as the "big four of Isan". The city is commonly known as Korat (, ), a shortened form of its name. It is the governmental seat of ...

lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of iguanodontian

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

(

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 ...

stage)

Khok Kruat Formation The Khok Kruat Formation () is a rock formation found in northeastern Thailand. It is the uppermost formation of the Khorat Group. It is dated to the Aptian stage of the Early Cretaceous period, and is notable for its fossils of dinosaurs. It ...

of Nakhon Ratchasima Province in northeastern

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 ...

. The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Ty ...

and only species is ''R. suranareae'', named after

Thao Suranari Thao Suranari ( th, ท้าวสุรนารี; 1771–1852) is the royally bestowed title of Lady Mo, also known as Ya Mo (, who was the wife of the deputy governor of Nakhon Ratchasima (Korat), the stronghold of Siamese control over ...

, a 19th-century war heroine. It was considered by one study to be a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

'', diagnosed with characters widespread in

Styracosterna Ankylopollexia is an extinct clade of ornithischian dinosaurs that lived from the Late Jurassic to the Late Cretaceous. It is a derived clade of iguanodontian ornithopods and contains the subgroup Styracosterna. The name stems from the Greek word ...

Discovery and naming

''Ratchasimasaurus'' was initially known as the “''

Probactrosaurus ''Probactrosaurus'' (meaning "before ''Bactrosaurus''") is an early herbivorous hadrosauroid iguanodont dinosaur. It lived in China during the Late Cretaceous period. Discovery and species In 1959 and 1960 a Soviet-Chinese expedition uncovered ...

''-like” iguanodontian and is only known from 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 ...

(specimen NRRU-A2064), a complete left dentary with no teeth that was found in the

in Thailand by a local farmer near a

pond A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from th ...

, likely around ; NRRU-A2064 was mentioned by Norman in 2004 in a phylogenenetic analysis.Norman, D.B. (2004). "Basal Iguanodontia." In D. B. Weishampel, P. Dodson, and H. Osmólska (eds.), The Dinosauria (2nd edition). University of California Press, Berkeley 413-437 The genus was named in 2011 by Shibata, Jintasakul & Azuma. The holotype is currently housed in The Northeastern Research Institute of Petrified Wood and Mineral Resources (NRIPM) and a mounted skeleton exists in River City,

Bangkok Bangkok, officially known in Thai language, Thai as Krung Thep Maha Nakhon and colloquially as Krung Thep, is the capital and most populous city of Thailand. The city occupies in the Chao Phraya River delta in central Thailand and has an estima ...

Description

One autapomorphy (unique characteristic) of ''Ratchasimasaurus'' is its elongated and flat ramus of the dentary. ''Ratchasimasaurus'' shows both primitive and derived characters for Iguanodontia, such as "a caudally inclined

coronoid process The Coronoid process (from Greek , "like a crown") can refer to: * The coronoid process of the mandible, part of the ramus mandibulae of the mandible * The coronoid process of the ulna The coronoid process of the ulna is a triangular process proj ...

and alveolar trough with a primitive crown impression, and a derived buccal shelf between the tooth row and the coronoid process". The length of the dentary is .

References

External links

Iguanodonts Aptian life Early Cretaceous dinosaurs of Asia Cretaceous Thailand Fossils of Thailand Fossil taxa described in 2011 Ornithischian genera {{ornithopod-stub