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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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Maxillary and dentary teeth of Sirindhorna.Isolated left maxillary teeth in labial (A; NRRU-A1959) and mesial (B) views (NRRU-A3630). An isolated dentary tooth (NRRU3001-28) in lingual (C) and distal (D) views. Lingual side of 4—5th preserved teeth of the dentary (NRRU3001-14) (E) and mammilations on denticles (F) on the apical edge from white squared area in E. Abbreviations: acc, accesory ridges; dnt, denticle; ml, mammilation; pr, primary ridge; sc, secondary ridge; t.f, facet for an adjacent tooth. Scale bars equal 5 mm.
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pone.0145904.g012: Maxillary and dentary teeth of Sirindhorna.Isolated left maxillary teeth in labial (A; NRRU-A1959) and mesial (B) views (NRRU-A3630). An isolated dentary tooth (NRRU3001-28) in lingual (C) and distal (D) views. Lingual side of 4—5th preserved teeth of the dentary (NRRU3001-14) (E) and mammilations on denticles (F) on the apical edge from white squared area in E. Abbreviations: acc, accesory ridges; dnt, denticle; ml, mammilation; pr, primary ridge; sc, secondary ridge; t.f, facet for an adjacent tooth. Scale bars equal 5 mm.

Mentions: Elements of the cranial skeleton have been discovered in disarticulation and suffered from pre-and postmortern deformation. Braincases and dentaries have several duplications that indicate an inclusion of at least four individuals. Nevertheless, those duplicated elements do not show any diagnosable characters as distinct taxa. We, therefore, considered iguanodontians bones described here as one taxon. Three articulated cranial bones and the dorsal potion of a braincase were known. NRRU3001-166 is the best-preserved skull. This specimen was originally separated into dorsal and ventral portions along with a horizontal breakage line running through the foramen for the trigeminal nerves (V) when it was found. The cranial portions rostral to the frontals are disarticulated and missing (Figs 2 and 3). The ventral process of the left postorbital, the left basipterygoid process and the left paroccipital process are broken. The right paroccipital process was missed when photographing, but this part was found later and added in the line drawing (Fig 2B and 2D). NRRU-A2035 is an almost complete braincase preserved with an articulated piece of left postorbital. Half of the right frontal, the left opisthostic-exoccipital complex, both side of the paroccipital process, a part of the prarasphenoid, basisphenoid and basioccipital are missing (Fig 4A and 4B). Descriptions of braincase include characters in this specimen. NRRU3001-65 and 179 are the dorsal half and the caudal part of braincases, respectively (Fig 4C and 4D). Although these two braincases show dorsal and caudal portions of brain cavities, we will report the detail structure of the braincase morphology of this new taxon in a separate paper. Other cranial parts: dermatocranium, mandible and teeth, are also described here (Figs 5–12). All measurements of bones are seen in Table 1.


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)

Maxillary and dentary teeth of Sirindhorna.Isolated left maxillary teeth in labial (A; NRRU-A1959) and mesial (B) views (NRRU-A3630). An isolated dentary tooth (NRRU3001-28) in lingual (C) and distal (D) views. Lingual side of 4—5th preserved teeth of the dentary (NRRU3001-14) (E) and mammilations on denticles (F) on the apical edge from white squared area in E. Abbreviations: acc, accesory ridges; dnt, denticle; ml, mammilation; pr, primary ridge; sc, secondary ridge; t.f, facet for an adjacent tooth. Scale bars equal 5 mm.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0145904.g012: Maxillary and dentary teeth of Sirindhorna.Isolated left maxillary teeth in labial (A; NRRU-A1959) and mesial (B) views (NRRU-A3630). An isolated dentary tooth (NRRU3001-28) in lingual (C) and distal (D) views. Lingual side of 4—5th preserved teeth of the dentary (NRRU3001-14) (E) and mammilations on denticles (F) on the apical edge from white squared area in E. Abbreviations: acc, accesory ridges; dnt, denticle; ml, mammilation; pr, primary ridge; sc, secondary ridge; t.f, facet for an adjacent tooth. Scale bars equal 5 mm.
Mentions: Elements of the cranial skeleton have been discovered in disarticulation and suffered from pre-and postmortern deformation. Braincases and dentaries have several duplications that indicate an inclusion of at least four individuals. Nevertheless, those duplicated elements do not show any diagnosable characters as distinct taxa. We, therefore, considered iguanodontians bones described here as one taxon. Three articulated cranial bones and the dorsal potion of a braincase were known. NRRU3001-166 is the best-preserved skull. This specimen was originally separated into dorsal and ventral portions along with a horizontal breakage line running through the foramen for the trigeminal nerves (V) when it was found. The cranial portions rostral to the frontals are disarticulated and missing (Figs 2 and 3). The ventral process of the left postorbital, the left basipterygoid process and the left paroccipital process are broken. The right paroccipital process was missed when photographing, but this part was found later and added in the line drawing (Fig 2B and 2D). NRRU-A2035 is an almost complete braincase preserved with an articulated piece of left postorbital. Half of the right frontal, the left opisthostic-exoccipital complex, both side of the paroccipital process, a part of the prarasphenoid, basisphenoid and basioccipital are missing (Fig 4A and 4B). Descriptions of braincase include characters in this specimen. NRRU3001-65 and 179 are the dorsal half and the caudal part of braincases, respectively (Fig 4C and 4D). Although these two braincases show dorsal and caudal portions of brain cavities, we will report the detail structure of the braincase morphology of this new taxon in a separate paper. Other cranial parts: dermatocranium, mandible and teeth, are also described here (Figs 5–12). All measurements of bones are seen in Table 1.

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