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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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The left maxilla (NRRU-A2048) of Sirindhorna.In lateral (A), ventral (B), medial (C), occulusal (D) views. Abbreviations: ect.fc, ectpterigoid facet; j.pr, jugal process; l. pr, lacrymal process; m.gr, maxillary grooves; nv.f, neurovascular foramen; pm.gr, premaxillary groove; rd.pr, rostrodorsal process; rv.pr, rostroventral process. Scale bar equals 10 cm.
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pone.0145904.g006: The left maxilla (NRRU-A2048) of Sirindhorna.In lateral (A), ventral (B), medial (C), occulusal (D) views. Abbreviations: ect.fc, ectpterigoid facet; j.pr, jugal process; l. pr, lacrymal process; m.gr, maxillary grooves; nv.f, neurovascular foramen; pm.gr, premaxillary groove; rd.pr, rostrodorsal process; rv.pr, rostroventral process. Scale bar equals 10 cm.

Mentions: The left maxilla (NRRU-A2048) is completely preserved (Fig 6). The rostral part of the maxilla is bifurcated and forms the rostrodorsal and rostroventral processes. The apex of the sub-triangular lacrimal (or ascending) process is located at the two fifths of the total length from the caudal end, and the rostrocaudally elongated maxillary body relative to the height of that apex make the maxilla a low-angled triangle-shape in lateral view (Fig 6A). The lateral surface of the maxilla bears several foramina and the rostral-most one is the largest. The ventral marginal line of the maxilla is almost straight and terminates in the rostroventral process. The bifurcated rostral part of maxilla forms a groove for the articulation of the maxillary process of the premaxilla, which becomes narrower toward the lacrimal process. There is no evidence of the antorbital fossa (fenestra), and the articular surface for the jugal is situated just caudal to the lacrimal process. The jugal process is missing its lateral projection, and probably does not form the long and robust caudolateral projection, which fits into a hollow formed in the medioventral surface of the rostral process of the jugal. The caudal end of the jugal process bears a deep groove running dorsoventrally that houses a foramen penetrating rostroventrally (Fig 6A). In dorsal view, the body of the maxilla is nearly straight, and the lateral and medial outlines of the maxilla run parallel (Fig 6B). There is the large ‘tongue’-shaped ectopterygoid facet caudal to the jugal process. In medial view, the medial surface of the maxilla bears an arched row of 24 subcircular neurovascular foramina, called “special foramina” (Fig 4C; [35]). A shallow groove connecting these adjacent foramina is inferred to be the accommodation of the dental lamina [35]. Caudomedial to the medial side of the rostrodorsal process, the maxillary grooves are weakly developed (Fig 6C). In ventral view, twenty-four alveoli are rostrocaudally arranged and slightly curved caudolaterally, and five of them preserve functional teeth (Fig 6D).


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)

The left maxilla (NRRU-A2048) of Sirindhorna.In lateral (A), ventral (B), medial (C), occulusal (D) views. Abbreviations: ect.fc, ectpterigoid facet; j.pr, jugal process; l. pr, lacrymal process; m.gr, maxillary grooves; nv.f, neurovascular foramen; pm.gr, premaxillary groove; rd.pr, rostrodorsal process; rv.pr, rostroventral process. Scale bar equals 10 cm.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0145904.g006: The left maxilla (NRRU-A2048) of Sirindhorna.In lateral (A), ventral (B), medial (C), occulusal (D) views. Abbreviations: ect.fc, ectpterigoid facet; j.pr, jugal process; l. pr, lacrymal process; m.gr, maxillary grooves; nv.f, neurovascular foramen; pm.gr, premaxillary groove; rd.pr, rostrodorsal process; rv.pr, rostroventral process. Scale bar equals 10 cm.
Mentions: The left maxilla (NRRU-A2048) is completely preserved (Fig 6). The rostral part of the maxilla is bifurcated and forms the rostrodorsal and rostroventral processes. The apex of the sub-triangular lacrimal (or ascending) process is located at the two fifths of the total length from the caudal end, and the rostrocaudally elongated maxillary body relative to the height of that apex make the maxilla a low-angled triangle-shape in lateral view (Fig 6A). The lateral surface of the maxilla bears several foramina and the rostral-most one is the largest. The ventral marginal line of the maxilla is almost straight and terminates in the rostroventral process. The bifurcated rostral part of maxilla forms a groove for the articulation of the maxillary process of the premaxilla, which becomes narrower toward the lacrimal process. There is no evidence of the antorbital fossa (fenestra), and the articular surface for the jugal is situated just caudal to the lacrimal process. The jugal process is missing its lateral projection, and probably does not form the long and robust caudolateral projection, which fits into a hollow formed in the medioventral surface of the rostral process of the jugal. The caudal end of the jugal process bears a deep groove running dorsoventrally that houses a foramen penetrating rostroventrally (Fig 6A). In dorsal view, the body of the maxilla is nearly straight, and the lateral and medial outlines of the maxilla run parallel (Fig 6B). There is the large ‘tongue’-shaped ectopterygoid facet caudal to the jugal process. In medial view, the medial surface of the maxilla bears an arched row of 24 subcircular neurovascular foramina, called “special foramina” (Fig 4C; [35]). A shallow groove connecting these adjacent foramina is inferred to be the accommodation of the dental lamina [35]. Caudomedial to the medial side of the rostrodorsal process, the maxillary grooves are weakly developed (Fig 6C). In ventral view, twenty-four alveoli are rostrocaudally arranged and slightly curved caudolaterally, and five of them preserve functional teeth (Fig 6D).

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