Ratchasimasaurus is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of non-hadrosaurid

Hadrosaurid

Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

 iguanodontian ornithopod

Ornithopod

Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs 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, and dominated the North American...

 dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 from Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

 (Aptian

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 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...

 stage) Khok Kruat Formation

Khok Kruat Formation

The Khok Kruat Formation is a rock formation found in northeastern Thailand. It is one of the formations of the Khorat Group. It is of Aptian stage , and is notable for its fossils of dinosaurs...

 of Nakhon Ratchasima Province

Nakhon Ratchasima Province

Nakhon Ratchasima or , often shortened to Korat or Khorat , is one of the north-eastern provinces of Thailand...

 in northeastern Thailand

Thailand

Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...

. 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

Coronoid process

The Coronoid process can refer to:* The coronoid process of the mandible, part of the ramus mandibulae of the mandible...

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