A new type of long-necked plant-eating dinosaur – the largest ever found in Southeast Asia – has been revealed in a study led by researchers at University College London (UCL), Mahasarakham University, Suranaree University of Technology and Sirindhorn Museum in Thailand.
The dinosaur, described in a new paper in the journal Scientific Reports, was identified from bones found at the edge of a pond in north-eastern Thailand 10 years ago.
Analysing spine, rib, pelvis and leg bones, including a front leg bone 1.78 metres long (as long as a human), the research team estimated that the dinosaur would have weighed 27 tonnes – about the same as nine adult Asian elephants – and measured 27 metres in length.
It has been named Nagatitan chaiyaphumensis, with "Naga" referring to a mythological aquatic serpent in Thai and Southeast Asian folklore, "Titan" referring to the giants of Greek mythology and chaiyaphumensis meaning "from Chaiyaphum", the Thai province where the fossils were discovered. It is the 14th dinosaur to be named in Thailand.
It belonged to the sauropod family of dinosaurs – long-necked, long-tailed plant-eaters that included the Diplodocus and Brontosaurus – and lived in the Early Cretaceous period between 100 and 120 million years ago.
Lead author Thitiwoot (Perth) Sethapanichsakul, a Thai PhD student at UCL Earth Sciences, said: "Our dinosaur is big by most people's standards – it likely weighed at least 10 tonnes more than Dippy the Diplodocus (Diplodocus carnegii). However, it is still dwarfed by sauropods like Patagotitan (60 tonnes) or Ruyangosaurus (50 tonnes).
"We refer to Nagatitan as 'the last titan' of Thailand. That is because it was discovered in Thailand's youngest dinosaur-bearing rock formation. Younger rocks laid down towards the end of the time of the dinosaurs are unlikely to contain dinosaur remains because the region by then had become a shallow sea. So this may be the last or most recent large sauropod we will find in Southeast Asia."
During the Early Cretaceous the environment would have been arid to semi-arid – a preferred habitat for sauropods who appeared to thrive in these environments, relying on the surface area of their long necks and tails to shed heat and regulate their body temperature.
The area where the specimens were found also appeared to be part of a meandering river system, which would have been home to fish, freshwater sharks and crocodiles.
Nagatitan would have lived alongside smaller plant-eating dinosaurs such as iguanodontians and early branching ceratopsians (cousins of the Triceratops), as well as big meat-eaters including carcharodontosaurians and spinosaurids, and flying reptiles called pterosaurs eating fish from the river.
Nagatitan was a somphospondylan sauropod – a subgroup of sauropod that became widespread about 120 million years ago. The authors found that it specifically belonged to a narrower group within the somphospondylans called Euhelopodidae, which represents a group of somphospondylan sauropods only found in Asia.
Nagatitan is distinct from other species due to a combination of unique features on its spine, pelvis and legs. A life-size reconstruction of the dinosaur is on display at the Thainosaur Museum at Asiatique in Bangkok.
Sethapanichsakul said: "My dream is to continue pushing to get Southeast Asian dinosaurs recognised internationally. 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.
"I've always been a dinosaur kid. This study doesn't just establish a new species but also fulfils a childhood promise of naming a dinosaur."
Co-author Professor Paul Upchurch, based at UCL Earth Sciences, said: "This discovery comes out of a new collaboration between UCL and colleagues in Thailand. The material was studied both in Thailand and at UCL - 3D scanning and printing has meant that we can study the specimen and collect data without having to travel (good for reducing carbon footprint).
"We have had a long-standing interest in the evolution of these gigantic plant eaters and have good collaborative links with researchers around the world. It is great to work with Thai colleagues and start to get insights into what was happening in Southeast Asia during the Jurassic and Cretaceous."
A team of five academics work on different aspects of dinosaur evolution at UCL, with strong collaborative links to the Natural History Museum. The extended research group comprises four research fellows and postdoc researchers, and more than 10 PhD students. At least four of the PhD students are working on dinosaur evolution, with the others looking at a wider array of other evolutionary questions relating to vertebrates, including crocodiles and birds.
Project leader and National Geographic Explorer Dr Sita Manitkoon, researcher at the Palaeontological Research and Education Centre, Mahasarakham University said: "Although Thailand is a small country within Asia, we have a very high diversity in dinosaur fossils, possibly the third most abundant in Asia in terms of dinosaur remains. We've only really been studying dinosaurs in Thailand about 40 years (since the first dinosaur was named in 1986), and already we have a surge of younger generation palaeontologists, who are actively undertaking research and promoting palaeontology and its importance within the country."
The new study received funding from the National Geographic Society.
