Paleontologists in northeastern Thailand have discovered a new species of mamenchisaurid sauropod dinosaur, revealing that this group of colossal dinosaurs, once believed to be primarily located in East Asia, also inhabited mainland Southeast Asia.
Reconstruction of a herd of Uragasaurus carasinensis in the Late Jurassic forests of Thailand, featuring rhymphorhynchoid pterosaurs and metricanthosaurid theropods. Image credit: Pakorn Chotchaiyaporn.
This newly identified dinosaur species, dubbed Uragasaurus carasinensis, thrived in what is now Thailand during the Late Jurassic period, approximately 150 to 145 million years ago.
Uragasaurus is part of the Mamenchisauridae family, renowned for their exceptionally long necks.
While Mamenchisauridae were common in China during the Middle to Late Jurassic, their presence in areas outside of China remains scarce.
“Mamenchisauridae represents a significant clade of non-neosauropod eusauropods from the Middle to Late Jurassic of East Asia,” said Dr. Apirut Nirupanapan of Mahasarakham University and his colleagues.
“Members of this clade are characterized by elongated cervical vertebrae with advanced pneumatic features, distinguishing them from other eusauropods, particularly in derived taxa.”
“Despite these traits evolving in various Cretaceous neosauropod lineages, including eupods and titanosaurs, they make interpreting the relationships within mamenchisaurids intricate, adding to the ongoing uncertainty regarding their phylogenetic placement among sauropods.”
The fossil record for mamenchisaurs is predominantly found in China, especially in the Sichuan Basin, where the Shaximi Formation provides an abundance of well-preserved Jurassic vertebrate fossils.
Uragasaurus carasinensis is primarily known from a single, remarkably preserved anterior dorsal vertebra, located just behind the dinosaur’s neck.
This specimen was unearthed from the Phu Noi Fossil Site within the Phu Kradung Formation, which is notable for yielding a rich diversity of Jurassic vertebrate fossils in Southeast Asia.
This vertebra, cataloged as PRC 460, was excavated alongside various other sauropod bone fragments, although these were not conclusively linked to the same individual.
Phylogenetic analysis places Uragasaurus carasinensis near the basal node of the mamenchisaurid family tree, indicating it may be one of the early diverging members of this group.
This discovery enriches the limited list of mamenchisaurids found outside of China, suggesting a broader geographic range and a more intricate evolutionary narrative than previously recognized.
The identification of Uragasaurus carasinensis marks “the first formally named mamenchisaurid from Thailand,” according to the paleontologists involved.
“This also extends the geographic reach of Mamenchisauridae into mainland Southeast Asia, further affirming that this clade was widespread across East Asia during the Late Jurassic,” they concluded.
“The presence of closely related taxa in China implies possible faunal connections throughout the East Asian continent during this era.”
“Comparative studies with more distantly located taxa highlight the complex paleobiogeographic dynamics of sauropods during the Jurassic-Cretaceous transition, but the limited fossil record complicates detailed reconstructions of dispersal pathways.”
“The phylogenetic positioning of Uragasaurus carasinensis at the base of Mamenchisauridae accentuates the morphological diversity present among the clade’s early divergent members.”
“Ongoing discoveries from the Phu Kradung Formation and other Jurassic sites in Southeast Asia could unveil critical insights into the initial evolutionary history and biogeographical dispersal of mamenchisaurid sauropods.”
The discovery of Uragasaurus carasinensis is detailed in a study published in the journal Scientific Reports.
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A. Nirupanapan et al. 2026. A new mamenchisaurid sauropod from the lower Phu Kradung Formation in the Upper Jurassic of northeastern Thailand. Scientific Reports 16, 21205; doi: 10.1038/s41598-026-49822-3
Source: www.sci.news
