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A New Basal Hadrosauroid Dinosaur from the Lower Cretaceous Khok Kruat Formation in Nakhon Ratchasima Province, Northeastern Thailand.

Shibata M, Jintasakul P, Azuma Y, You HL - PLoS ONE (2015)

Bottom Line: The new taxon is based on composite skull and mandible including premaxilla, maxilla, jugal, quadrate, braincases, predentary, dentaries, surangular, and maxillary and dentary teeth.Phylogenetic analysis revealed S. khoratensis as among the most basal hadrosauroids.Sirindhorna khoratensis is the best-preserved iguanodontian ornithopod in Southeast Asia and sheds new light to resolve the evolution of basal hadrosauriforms.

View Article: PubMed Central - PubMed

Affiliation: Institute of Dinosaur Research, Fukui Prefectural University, 4-1-1 Kenjojima, Matsuoka, Eiheiji-Cho, Fukui, 910-1195, Japan.

ABSTRACT
A new basal hadrosauroid dinosaur from the Lower Cretaceous Khok Kruat Formation of Thailand, Sirindhorna khoratensis gen. et sp. nov is described. The new taxon is based on composite skull and mandible including premaxilla, maxilla, jugal, quadrate, braincases, predentary, dentaries, surangular, and maxillary and dentary teeth. It is diagnostic by such characters as, sagittal crest extending along entire dorsal surface of the parietal and reaching the frontoparietal suture (autapomorphy), transversely straight frontoparietal suture, caudodorsally faced supraoccipital, no participation of the supraoccipital in the foramen magnum, mesiodistally wide leaf-shaped dentary tooth with primary and secondary ridges on the lingual surface of the crown, perpendicularly-erected and large coronoid process of dentary, and nonvisible antorbital fossa of the maxilla in lateral view. Phylogenetic analysis revealed S. khoratensis as among the most basal hadrosauroids. Sirindhorna khoratensis is the best-preserved iguanodontian ornithopod in Southeast Asia and sheds new light to resolve the evolution of basal hadrosauriforms.

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Locality map and stratigraphic column for Sirindhorna.(A) Map of Nakhon Ratchasima Province, Thailand, (B) localities of Sirindhorna (star mark), Ratchasimasuarus (R) and Siamodon (S), (C) stratigraphic column for the Khorat Group (after [19]).
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pone.0145904.g001: Locality map and stratigraphic column for Sirindhorna.(A) Map of Nakhon Ratchasima Province, Thailand, (B) localities of Sirindhorna (star mark), Ratchasimasuarus (R) and Siamodon (S), (C) stratigraphic column for the Khorat Group (after [19]).

Mentions: Since 2007, the collaborative research project (JTDP) between Fukui Prefectural Dinosaur Museum (FPDM), Japan and the Northeastern Research Institute of Petrified Woods and Mineral Resources, Nakhon Ratchasima Rajabhat University (NRRU), Thailand, have uncovered abundant vertebrate fossils from a site in the Lower Cretaceous Khok Kruat Formation in Suranaree Subdistrict, Muaeng Nakhon Ratchasima District, Nakhon Ratchasima (Fig 1). The Khok Kruat Formation is the uppermost unit of the Khorat Group and is distributed widely in the Khorat Basin of northeastern Thailand [18]. This formation consists of siltstone, mudstone, sandstone and conglomerate including calcareous nodules, and was deposited in the meandering river under the semi-arid to arid environment [18–20]. The precise age of this formation has not been determined yet due to lack of diagnostic index fossils to date. However, no direct information from the Khok Kruat Formation was obtained to corroborate this age in [21]. Traditionally, an Aptian age is accepted for this formation based on palynological data, the occurrences of the fresh water hybodont shark Thaiodus ruchae and the basal ceratopsian Psittacosaurus sattayaraki, and the age of the overlying Maha Sarakham Formation (Albian–Cenomanian) [20, 22–24]. We follow the Aptian age determination in this study (Fig 1C).


A New Basal Hadrosauroid Dinosaur from the Lower Cretaceous Khok Kruat Formation in Nakhon Ratchasima Province, Northeastern Thailand.

Shibata M, Jintasakul P, Azuma Y, You HL - PLoS ONE (2015)

Locality map and stratigraphic column for Sirindhorna.(A) Map of Nakhon Ratchasima Province, Thailand, (B) localities of Sirindhorna (star mark), Ratchasimasuarus (R) and Siamodon (S), (C) stratigraphic column for the Khorat Group (after [19]).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4696827&req=5

pone.0145904.g001: Locality map and stratigraphic column for Sirindhorna.(A) Map of Nakhon Ratchasima Province, Thailand, (B) localities of Sirindhorna (star mark), Ratchasimasuarus (R) and Siamodon (S), (C) stratigraphic column for the Khorat Group (after [19]).
Mentions: Since 2007, the collaborative research project (JTDP) between Fukui Prefectural Dinosaur Museum (FPDM), Japan and the Northeastern Research Institute of Petrified Woods and Mineral Resources, Nakhon Ratchasima Rajabhat University (NRRU), Thailand, have uncovered abundant vertebrate fossils from a site in the Lower Cretaceous Khok Kruat Formation in Suranaree Subdistrict, Muaeng Nakhon Ratchasima District, Nakhon Ratchasima (Fig 1). The Khok Kruat Formation is the uppermost unit of the Khorat Group and is distributed widely in the Khorat Basin of northeastern Thailand [18]. This formation consists of siltstone, mudstone, sandstone and conglomerate including calcareous nodules, and was deposited in the meandering river under the semi-arid to arid environment [18–20]. The precise age of this formation has not been determined yet due to lack of diagnostic index fossils to date. However, no direct information from the Khok Kruat Formation was obtained to corroborate this age in [21]. Traditionally, an Aptian age is accepted for this formation based on palynological data, the occurrences of the fresh water hybodont shark Thaiodus ruchae and the basal ceratopsian Psittacosaurus sattayaraki, and the age of the overlying Maha Sarakham Formation (Albian–Cenomanian) [20, 22–24]. We follow the Aptian age determination in this study (Fig 1C).

Bottom Line: The new taxon is based on composite skull and mandible including premaxilla, maxilla, jugal, quadrate, braincases, predentary, dentaries, surangular, and maxillary and dentary teeth.Phylogenetic analysis revealed S. khoratensis as among the most basal hadrosauroids.Sirindhorna khoratensis is the best-preserved iguanodontian ornithopod in Southeast Asia and sheds new light to resolve the evolution of basal hadrosauriforms.

View Article: PubMed Central - PubMed

Affiliation: Institute of Dinosaur Research, Fukui Prefectural University, 4-1-1 Kenjojima, Matsuoka, Eiheiji-Cho, Fukui, 910-1195, Japan.

ABSTRACT
A new basal hadrosauroid dinosaur from the Lower Cretaceous Khok Kruat Formation of Thailand, Sirindhorna khoratensis gen. et sp. nov is described. The new taxon is based on composite skull and mandible including premaxilla, maxilla, jugal, quadrate, braincases, predentary, dentaries, surangular, and maxillary and dentary teeth. It is diagnostic by such characters as, sagittal crest extending along entire dorsal surface of the parietal and reaching the frontoparietal suture (autapomorphy), transversely straight frontoparietal suture, caudodorsally faced supraoccipital, no participation of the supraoccipital in the foramen magnum, mesiodistally wide leaf-shaped dentary tooth with primary and secondary ridges on the lingual surface of the crown, perpendicularly-erected and large coronoid process of dentary, and nonvisible antorbital fossa of the maxilla in lateral view. Phylogenetic analysis revealed S. khoratensis as among the most basal hadrosauroids. Sirindhorna khoratensis is the best-preserved iguanodontian ornithopod in Southeast Asia and sheds new light to resolve the evolution of basal hadrosauriforms.

Show MeSH
Related in: MedlinePlus