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| Uragasaurus kalasinensis Nilpanapan, Manitkoon, Suteethorn & Lauprasert, 2026 อุรคาซอรัส กาฬสินธุ์เอนซิส || DOI: doi.org/10.1038/s41598-026-49822-3 Artwork by Pakorn Chotchaiyaporn (Jæsica ẞababi). |
Abstract
Mamenchisauridae is a group of long-necked non-neosauropodan eusauropod dinosaurs that were abundant in East Asia during the Middle to Late Jurassic, but their diversity and geographic distribution outside China remain poorly documented. Here we describe Uragasaurus kalasinensis gen. et sp. nov., a new sauropod dinosaur from the Phu Kradung Formation of northeastern Thailand. The new taxon is based on a well-preserved anterior dorsal vertebra exhibiting a distinctive combination of characters, including a unique Y-shaped configuration formed by the intraprezygapophyseal and single intraprezygapophyseal laminae and a camellate internal pneumatic structure within the centrum revealed by computed tomography (CT). Phylogenetic analyses recover the new taxon as an early-diverging member of Mamenchisauridae. This discovery represents the first formally named mamenchisaurid from Thailand and expands the known geographic distribution of the clade in Southeast Asia. The occurrence of this taxon in the Lower part of the Phu Kradung Formation also contributes to understanding faunal succession within the unit, supports an Upper Jurassic age for the lower part of the formation, and improves understanding of sauropod diversity in Southeast Asia during the Jurassic-Cretaceous transition.
Keywords: Sauropoda, Mamenchisauridae, Upper Jurassic, Phu Kradung Formation, Northeastern Thailand
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| Holotype of Uragasaurus kalasinensis (PRC 460) and associated materials in the quarry map. PRC 460 Anterior dorsal vertebra in anterior view (a), KS 34-581 anterior dorsal neural arch in anterior view (b), KS 34-602a middle cervical vertebra in ventral view (c), KS 34-586 anterior dorsal neural arch in anterior view, attached by KS 34-588 fibula (d), KS 34-587 coracoid in lateral view (e), KS 34-602b right cervical rib in lateral view (f). |
Uragasaurus kalasinensis gen. et sp. nov.
อุรคาซอรัส กาฬสินธุ์เอนซิส
Holotype: The isolated anterior dorsal vertebra PRC 460 has been housed at the Palaeontological Research and Education Centre (PRC), Mahasarakham University, Thailand. Following standard paleontological protocols, the vertebrae were mechanically prepared using pneumatic tools and fine brushes to remove the surrounding sediment matrix.
Locality: Phu Noi Locality, Kalasin Province, northeastern Thailand (16.93298° N, 103.72327° E).
Horizon: Lower part of the Phu Kradung Formation, Khorat Group.
Age: Latest Jurassic, based on regional stratigraphic correlations and the composition of the vertebrate assemblage; precise chronostratigraphic constraints remain uncertain.
Diagnosis: Uragasaurus kalasinensis gen. et sp. nov. is a mamenchisaurid sauropod diagnosed by the following unique combination of characters (autapomorphy is marked by *): (1) anterior dorsal vertebra with prominent, elongated teardrop-shaped pneumatic fossae on the distal portion of the transverse processes*; (2) intraprezygapophyseal laminae (tprl) meeting ventromedially to form a Y-shaped configuration in anterior view, incorporating a single vertical intraprezygapophyseal lamina (stprl); and (3) shallow, subtriangular pleurocoel lacking an internal septum.
Etymology: The genus name “Uraga” originates from the Sanskrit word उरग, meaning “snake” or “serpent”, referring to the distinguished long neck of the family. The term “saurus” is derived from the Greek word saûros, meaning lizard. The specific epithet refers to Kalasin Province, where the specimens are from.
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| Holotype of Uragasaurus kalasinensis (PRC 460) and associated materials in the quarry map. PRC 460 Anterior dorsal vertebra in anterior view (a), KS 34-581 anterior dorsal neural arch in anterior view (b), KS 34-602a middle cervical vertebra in ventral view (c), KS 34-586 anterior dorsal neural arch in anterior view, attached by KS 34-588 fibula (d), KS 34-587 coracoid in lateral view (e), KS 34-602b right cervical rib in lateral view (f). Quarry map showing the spatial distribution of the holotype and associated materials from the Phu Noi Locality (g). PRC 460, representing the new taxon Uragasaurus kalasinensis, is indicated in red. Associated sauropod elements include KS 34-586, KS 34-587, KS 34-588, and KS 34-602a–b, highlighted in yellow, green, blue, purple, and pink, respectively. The inset shows a close-up of the excavation grid highlighting the relative positions of the holotype and nearby associated materials. Each grid square represents 0.75 × 0.75 m. |
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| Life reconstruction of a herd of five individuals of Uragasaurus kalasinensis inhabiting a Late Jurassic forest in Thailand, accompanied by a pair of rhamphorhynchoid pterosaurs and a metriacanthosaurid theropod. Artwork by Pakorn Chotchaiyaporn (Jæsica ẞababi). |
Apirut Nilpanapan, Sita Manitkoon, Varavudh Suteethorn and Komsorn Lauprasert. 2026. A New mamenchisaurid Sauropod from the Lower Phu Kradung Formation, Upper Jurassic of northeastern Thailand. Scientific Reports. 16: 21205. DOI: doi.org/10.1038/s41598-026-49822-3 [08 July 2026]