A uniquely shaped bone has revealed that a certain long-necked dinosaur used to roam across Thailand. This dinosaur, Uragasaurus kalasinensis, belongs to a family of sauropods known as Mamenchisauridae; fossils from this group have rarely been unearthed outside of China, but the discovery of U. kalasinensis based on a single vertebra from northeastern Thailand shows that these Jurassic-era dinos may have been more widespread than initially believed.
A new study published in Scientific Reports describes U. kalasinensis from just one bone with several intriguing features — the vertebra (a bone in the spinal column) has a Y-shape that’s unique to the species, and it contains small hollow chambers that would’ve reduced its weight, helping the dinosaur support its long neck.
Thailand's Newest Sauropod
Uragasaurus kalasinensis fossils
Photo Credit: Photography by Apirut Nilpanapan
Most mamenchisaurid fossils, dated to around the Middle to Late Jurassic, come from the Sichuan Basin in southwestern China. The first fossil from this dinosaur family, belonging to the species Mamenchisaurus constructus, was found at a construction site in 1952, and since then, several other species have been discovered in the region.
More recently, mamenchisaurid fossils have begun to appear outside China. Vertebrae from Tanzania that were originally assigned to another Late Jurassic sauropod, Janenschia robusta, were found to belong instead to a mamenchisaurid, indicating that the dinosaur family lived in Africa as well as Asia.
U. kalasinensis now represents the first formally named mamenchisaurid sauropod from northeastern Thailand. The scientific name includes a reference to the Sanskrit word for “snake” or “serpent” (“Uraga”) and Thailand’s Kalasin province, where the species was discovered.
The discovery was made when paleontologists found an anterior dorsal vertebra (near the head) in the middle section of the Phu Kradung rock formation.
"Combined with other material from the Phu Kradung Formation, it reveals that Southeast Asia was an important center of mamenchisaurid diversity, filling a critical gap in understanding the biogeographic distribution and evolutionary radiation of this sauropod group across the Asian continent during the Jurassic period,” study author Komsorn Lauprasert, a paleontology professor at Thailand’s Mahasarakham University, told Discover.
Read More: Jurassic Predators Feasted on Baby Long-Necked Dinosaurs 150 Million Years Ago
An Air-Filled Vertebra
The well-preserved vertebra of U. kalasinensis had a Y-shaped configuration, which is considered a unique morphological feature of the species, according to the study.
Researchers used CT scans to detect other notable features of the vertebra; it was marked with elongated teardrop-shaped fossae, which are prominent depressions or concavities in bones, according to the Florida Museum. CT data also revealed the pneumatic structure of the vertebra, meaning the bone has air-filled chambers.
A pneumatic structure is present in most sauropod vertebrae, including those of mamenchisaurids. According to a 2025 study in Cretaceous Research, the hollowed-out vertebral columns of sauropods contain extensive air sac systems, similar to those of living birds.
This structure reduces bone density in sauropods, allowing them to support their necks properly. The hollow vertebrae would’ve also decreased mechanical stress in sauropods’ necks.
The Longest Necks in Natural History
Other kinds of dinosaurs had pneumatic vertebrae, too, including theropods and pterosaurs. However, their necks didn’t get anywhere near the length of sauropod necks. According to a 2013 study in PeerJ, theropods had necks only about 6 feet to 8 feet long; some pterosaurs had necks up to 9 feet long, but the largest sauropods had them beat, with one boasting a neck over 50 feet long.
Uragasaurus kalasinensis being scanned.
(Photo Credit: Photography by Apirut Nilpanapan)
Many birds retain these pneumatic vertebrae; meanwhile, the most iconic long-necked animal today, the giraffe, lacks the air-sac system and pneumatic vertebrae found in these birds.
U. kalasinensis, along with other mamenchisaurids, was able to evolve such long necks in part because of the structure of their vertebrae. The study authors write that U. kalasinensis, with its geographic distribution now expanded into Thailand, could be an important piece in describing sauropod diversity during the transition from the Late Jurassic to the Early Cretaceous.
"Given Thailand's extensive Jurassic sedimentary deposits and limited paleontological exploration compared to China, future excavations will likely uncover more mamenchisaurid specimens, potentially revealing new species,” Lauprasert said.
Read More: 155-Million-Year-Old Dinosaur May Be the First Jurassic Brachiosaurid Found in South America
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Scientific Reports: A new mamenchisaurid sauropod from the Lower Phu Kradung Formation, Upper Jurassic of northeastern Thailand
- This article references information from the Florida Museum: Florida Vertebrate Fossils
- This article references information from a study published in Cretaceous Research: Pneumatic structures of sauropod cervical vertebrae from the Lower Cretaceous Sao Khua Formation of northeastern Thailand
- This article references information from a study published in PeerJ: Why sauropods had long necks; and why giraffes have short necks
