Nagatitan chaiyaphumensis: Thailand’s largest dinosaur found in Southeast Asia

Over the past four decades, palaeontologists in Thailand have revealed an exceptionally rich and varied prehistoric past.

A decade ago, bones were discovered beside a pond in north-east Thailand. Researchers spent the following ten years establishing what they belonged to.

Although dinosaur bones occur frequently in older Thai rocks, they are exceptionally scarce in the younger, 110-million-year-old layer that yielded this partial skeleton.

The remains came from a previously undescribed species: a giant plant-eater weighing as much as nine Asian elephants and measuring 27 metres from head to tail.

It has now been confirmed as the largest dinosaur ever discovered in Southeast Asia.

The fossils were found in Chaiyaphum province in north-east Thailand. Thitiwoot Sethapanichsakul, a PhD student at University College London (UCL), led the research.

Meet Nagatitan chaiyaphumensis

Nagatitan chaiyaphumensis was a sauropod, part of the same broad family as Diplodocus and Brontosaurus. This vast plant-eating dinosaur had a long neck and tail.

It lived during the Early Cretaceous, between 100 and 120 million years ago, in an arid to semi-arid landscape traversed by winding rivers.

Its name draws on several traditions. In Thai and Southeast Asian folklore, Naga is a mythical water serpent; Titan comes from Greek mythology; and chaiyaphumensis means “from Chaiyaphum”.

It is the 14th dinosaur to receive a formal name in Thailand.

The researchers studied bones from the spine, ribs, pelvis and legs. One front leg bone alone was 1.78 metres long. Using the remains, they estimated that the dinosaur measured 27 metres in total and weighed 27 tonnes.

“Our dinosaur is big by most people’s standards – it likely weighed at least 10 tonnes more than Dippy the Diplodocus,” Sethapanichsakul said. “However, it is still dwarfed by sauropods like Patagotitan (60 tonnes) or Ruyangosaurus (50 tonnes).”

The mystery of the last titan

Nagatitan chaiyaphumensis is a member of Euhelopodidae, a subgroup of sauropods found exclusively in Asia. A particular combination of characteristics in its spine, pelvis and legs distinguishes it from the group’s other members.

The fossils were recovered from Thailand’s youngest dinosaur-bearing rock formation, the most recently deposited layer in the country known to contain dinosaur remains.

No such remains have been found in the rocks above. When those later layers formed, the area had become a shallow sea, and the animals that had once lived there disappeared from the fossil record without a trace.

“We refer to Nagatitan chaiyaphumensis as ‘the last titan’ of Thailand,” Sethapanichsakul said. “This may be the last or most recent large sauropod we will find in Southeast Asia.”

Ancient rivers and giant predators

The hot, dry climate of Thailand in the Early Cretaceous was especially well suited to sauropods.

Their long necks and tails did more than help them strip vegetation from tall trees: they also helped the animals release body heat.

The rivers near the fossil site would have teemed with fish, freshwater sharks and crocodiles.

On land, Nagatitan chaiyaphumensis lived alongside smaller herbivores, including iguanodontians and early relatives of Triceratops, as well as large predatory dinosaurs such as carcharodontosaurians and spinosaurids. Nagatitan was by far the biggest animal in that ecosystem.

A growing dinosaur hotspot

Thailand has formally studied its dinosaurs for only about 40 years, since the first was named in 1986. Yet in that time, it has developed what may be Asia’s third most diverse dinosaur fossil record.

“Although Thailand is a small country within Asia, we have a very high diversity in dinosaur fossils,” said project leader Sita Manitkoon of Mahasarakham University.

“We’ve already seen a surge of younger-generation palaeontologists actively undertaking research and promoting palaeontology and its importance within the country.”

More dinosaur hunting in Thailand

The team still has a substantial collection of sauropod fossils awaiting formal description. Some could belong to species new to science, so more discoveries may follow.

“My dream is to continue pushing to get Southeast Asian dinosaurs recognised internationally,” Sethapanichsakul said.

“More international collaborations between Thailand and other institutions like UCL can further our understanding of the region’s palaeobiology and apply it to a global context.”

“This all starts with identifying and describing the specimens we have found first. We have a large collection of sauropod fossils that have not yet been formally described – these may include a number of new species,” he said.

A life-size reconstruction is now on display at the Thainosaur Museum at Asiatique in Bangkok.