Sometimes, one bone is enough.

Researchers in Thailand have identified a new species of giant dinosaur from a single vertebra found in the Phu Kradung Formation, a fossil bed in northeastern Thailand. The dinosaur has been named Uragasaurus kalasinensis.

It was a long-necked sauropod, the group of giant plant-eating dinosaurs that includes Diplodocus and Brontosaurus, and lived in forests in Southeast Asia just before the Jurassic-Cretaceous transition, which began around 143 million years ago.

It is also the first formally named member of the long-necked dinosaur family Mamenchisauridae from northeastern Thailand.

“This discovery expands the known diversity of mamenchisaurid sauropods in Southeast Asia and provides new information on the geographic distribution and evolutionary history of the clade,” writes a team led by paleontologist Apirut Nilpanapan of Mahasarakham University in Thailand.

The findings were published in Scientific Reports.

The vertebra was found in the Phu Kradung Formation, which formed over millions of years as a system of rivers deposited sediment and debris on a floodplain. The formation has yielded little more than fragments, with few confident identifications.

Researchers said visual examination and CT scans showed the fossil had a combination of features not seen in any other species. They pointed to the position and shape of air pockets left by the dinosaur’s respiratory system inside the fossil, along with an unusual Y-shaped arrangement of bony ridges on the exterior.

Several other sauropod bones were found nearby, including a fibula, coracoid, cervical vertebrae and other vertebrae. The researchers said those bones may have belonged to the same species, but none preserved features distinctive enough to confidently assign them to Uragasaurus.

Only the original vertebra had the anatomical features needed to diagnose a new species.

The researchers also said the fossil showed the dinosaur belonged to the mamenchisaurids, a family whose fossils have mostly been found in China. Uragasaurus shows the family was also present in what is now Southeast Asia during the Late Jurassic.

“Continued discoveries from the Phu Kradung Formation and other Jurassic deposits in Southeast Asia may therefore provide important insights into the early evolutionary history and biogeographic dispersal of mamenchisaurid sauropods,” the researchers write.

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