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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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Related in: MedlinePlus

Comparisons with other Thailand iguanodontians.(A) Holotypic left maxilla of Siamodon (after [16]), (B) holotypic right dentary of Ratchasimasaurus (from [17]), (C) left maxilla of Sirindhorna (NRRU-A2048), (D) left dentary of Sirindhorna (NRRU3001-167). Scale bars equal 10 cm.
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pone.0145904.g015: Comparisons with other Thailand iguanodontians.(A) Holotypic left maxilla of Siamodon (after [16]), (B) holotypic right dentary of Ratchasimasaurus (from [17]), (C) left maxilla of Sirindhorna (NRRU-A2048), (D) left dentary of Sirindhorna (NRRU3001-167). Scale bars equal 10 cm.

Mentions: Two hadrosauroids have been previously known from the Khok Kruat Formation: Siamodon nimingami [16] and Ratchasimasaurus suranareae [17] (Fig 15). Siamodon was based upon an isolated maxilla. Although this maxilla was supposed to have been found in Ban Saphan Hin, one of the authors (PJ) insisted that the locality is Ban Nong Rangka, located in the adjacent subdistrict (Fig 1). The isosceles-shaped maxilla of Siamodon is distinct from the low triangle shape of that of Sirindhorna (Fig 15A and 15C). Ratchasimasaurus, on the other hand, is known only from one dentary, which is characterized with a low and elongate dentary ramus and the robust coronoid process. The morphology of Ratchasimasaurs is unique among iguanodontians and is evidently distinguishable from that of Sirindhorna (Fig 15B and 15D). Consequently, Sirindhorna khoratensis is regarded as a valid genus and species.


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)

Comparisons with other Thailand iguanodontians.(A) Holotypic left maxilla of Siamodon (after [16]), (B) holotypic right dentary of Ratchasimasaurus (from [17]), (C) left maxilla of Sirindhorna (NRRU-A2048), (D) left dentary of Sirindhorna (NRRU3001-167). Scale bars equal 10 cm.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0145904.g015: Comparisons with other Thailand iguanodontians.(A) Holotypic left maxilla of Siamodon (after [16]), (B) holotypic right dentary of Ratchasimasaurus (from [17]), (C) left maxilla of Sirindhorna (NRRU-A2048), (D) left dentary of Sirindhorna (NRRU3001-167). Scale bars equal 10 cm.
Mentions: Two hadrosauroids have been previously known from the Khok Kruat Formation: Siamodon nimingami [16] and Ratchasimasaurus suranareae [17] (Fig 15). Siamodon was based upon an isolated maxilla. Although this maxilla was supposed to have been found in Ban Saphan Hin, one of the authors (PJ) insisted that the locality is Ban Nong Rangka, located in the adjacent subdistrict (Fig 1). The isosceles-shaped maxilla of Siamodon is distinct from the low triangle shape of that of Sirindhorna (Fig 15A and 15C). Ratchasimasaurus, on the other hand, is known only from one dentary, which is characterized with a low and elongate dentary ramus and the robust coronoid process. The morphology of Ratchasimasaurs is unique among iguanodontians and is evidently distinguishable from that of Sirindhorna (Fig 15B and 15D). Consequently, Sirindhorna khoratensis is regarded as a valid genus and species.

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