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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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Right jugal (NRRU3001-7) and quadrate (NRRU3001-175) of Sirindhorna.The right jugal in lateral (A), medial (B) views. The right quadrate in lateral (C),caudal (D), and distal (E) views. Abbreviations: d.pr, dorsal process; ect.fc, ectpterigoidal facet; l.fc, lacrymal facet; m.fc, maxillary facet; po.st, postorbital suture; pt.w, pterygoid wing; q.f, quadrate foramen; r.pr, rostral process. Scale bar equals 10 cm.
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pone.0145904.g007: Right jugal (NRRU3001-7) and quadrate (NRRU3001-175) of Sirindhorna.The right jugal in lateral (A), medial (B) views. The right quadrate in lateral (C),caudal (D), and distal (E) views. Abbreviations: d.pr, dorsal process; ect.fc, ectpterigoidal facet; l.fc, lacrymal facet; m.fc, maxillary facet; po.st, postorbital suture; pt.w, pterygoid wing; q.f, quadrate foramen; r.pr, rostral process. Scale bar equals 10 cm.

Mentions: The right jugal (NRRU3001-7) is almost complete, lacking only the dorsal tip of the caudal process (Fig 7A and 7B). The triradiate jugal consists of three processes: a rostral process that contacts the maxilla and the lacrimal, a dorsal process that articulates with the postorbital, and a caudal process that meets the quadratojugal. The ventral border of the jugal is weakly bowed. The rostral process of the jugal is slightly curved rostrodorsally and does not deepen dorsoventrally. The rostral process terminates in the articular facets for the lacrimal on the lateral aspect and for the maxilla on the medial side. The dorsal process of the jugal extends almost perpendicular to the long axis of the jugal and ends at the articular facet for the postorbital, becoming broader mediolaterally. A lateral skirt of the dorsal process covers the jugal process of the postorbital in articulaton. In medial view, the rostral process bears the medially facing articular facet for the maxilla, which is heavily striated and separated into two fossae at its caudal end (Fig 7B). This facet deepens caudally and extends into the interior of the jugal, lateral to the facet for the ectopterygoid. The facet for the ectopterygoid is deep and oval-shaped, and positioned just rostral to the base of the dorsal process (Fig 7B). This facet is bounded just caudal to the facet for the maxilla by a thin ridge. The mediolaterally thin caudal process becomes dorsoventrally deep caudally and bears a shallow and broad facet for the quadratojugal.


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)

Right jugal (NRRU3001-7) and quadrate (NRRU3001-175) of Sirindhorna.The right jugal in lateral (A), medial (B) views. The right quadrate in lateral (C),caudal (D), and distal (E) views. Abbreviations: d.pr, dorsal process; ect.fc, ectpterigoidal facet; l.fc, lacrymal facet; m.fc, maxillary facet; po.st, postorbital suture; pt.w, pterygoid wing; q.f, quadrate foramen; r.pr, rostral process. Scale bar equals 10 cm.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0145904.g007: Right jugal (NRRU3001-7) and quadrate (NRRU3001-175) of Sirindhorna.The right jugal in lateral (A), medial (B) views. The right quadrate in lateral (C),caudal (D), and distal (E) views. Abbreviations: d.pr, dorsal process; ect.fc, ectpterigoidal facet; l.fc, lacrymal facet; m.fc, maxillary facet; po.st, postorbital suture; pt.w, pterygoid wing; q.f, quadrate foramen; r.pr, rostral process. Scale bar equals 10 cm.
Mentions: The right jugal (NRRU3001-7) is almost complete, lacking only the dorsal tip of the caudal process (Fig 7A and 7B). The triradiate jugal consists of three processes: a rostral process that contacts the maxilla and the lacrimal, a dorsal process that articulates with the postorbital, and a caudal process that meets the quadratojugal. The ventral border of the jugal is weakly bowed. The rostral process of the jugal is slightly curved rostrodorsally and does not deepen dorsoventrally. The rostral process terminates in the articular facets for the lacrimal on the lateral aspect and for the maxilla on the medial side. The dorsal process of the jugal extends almost perpendicular to the long axis of the jugal and ends at the articular facet for the postorbital, becoming broader mediolaterally. A lateral skirt of the dorsal process covers the jugal process of the postorbital in articulaton. In medial view, the rostral process bears the medially facing articular facet for the maxilla, which is heavily striated and separated into two fossae at its caudal end (Fig 7B). This facet deepens caudally and extends into the interior of the jugal, lateral to the facet for the ectopterygoid. The facet for the ectopterygoid is deep and oval-shaped, and positioned just rostral to the base of the dorsal process (Fig 7B). This facet is bounded just caudal to the facet for the maxilla by a thin ridge. The mediolaterally thin caudal process becomes dorsoventrally deep caudally and bears a shallow and broad facet for the quadratojugal.

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