Ratchasimasaurus Temporal range: Aptian ~120–113 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Mounted skeleton
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Ornithopoda
Clade:	†Iguanodontia
Genus:	†Ratchasimasaurus Shibata, Jintasakul, & Azuma, 2011
Type species
†Ratchasimasaurus suranareae Shibata, Jintasakul, & Azuma, 2011

Ratchasimasaurus (meaning "Nakhon Ratchasima lizard") is a genus of iguanodontian ornithopod dinosaur from Early Cretaceous (Aptian stage) Khok Kruat Formation of Nakhon Ratchasima Province in northeastern Thailand. The type and only species is R. suranareae, named after Thao Suranari, a 19th-century war heroine.^[1] It was considered by one study to be a nomen dubium, diagnosed with characters widespread in Styracosterna.^[2]

Discovery and naming

Ratchasimasaurus was initially known as the “Probactrosaurus-like” iguanodontian and is only known from the holotype (specimen NRRU-A2064), a complete left dentary with no teeth that was found in the Khok Kruat Formation in Thailand by a local farmer near a pond,^[1] likely around c. 2002 – c. 2004; NRRU-A2064 was mentioned by Norman in 2004 in a phylogenenetic analysis.^[3] The genus was named in 2011 by Shibata, Jintasakul & Azuma.^[1] 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.

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 and alveolar trough with a primitive crown impression, and a derived buccal shelf between the tooth row and the coronoid process".^[1] The length of the dentary is 198.1 millimetres (7.80 in).^[1]