A colossal plant-eating dinosaur, measuring nearly 90 feet (27 meters) long, once roamed the warm, arid landscapes of what is now Thailand approximately 113 million years ago.
This newly identified behemoth, named Nagatitan chaiyaphumensis, represents the largest-known dinosaur discovered in Southeast Asia.
Researchers have unearthed significant skeletal remains of Nagatitan, a member of the sauropod lineage characterized by their distinctive long necks, lengthy tails, small heads, and four columnar legs.
The fossils of this Cretaceous Period giant were initially spotted by a local villager in Thailand’s northeastern Chaiyaphum province.
Over several years, scientists meticulously excavated various bones, including spine, rib, pelvis, and leg bones, notably a humerus (front leg bone) measuring an impressive 5.8 feet (1.78 meters) long.
Based on the dimensions of its humerus and femur, the corresponding hind leg bone, researchers estimate Nagatitan’s body mass to have been between 25 and 28 tons.
While its head and teeth were not recovered, its feeding habits are inferred from other sauropods.
“Nagatitan was probably a bulk browser that focused on consuming high volumes of vegetation that required little to no chewing such as conifers and possibly seed ferns,” explained Thitiwoot Sethapanichsakul, a University College London doctoral student in palaeontology and lead author of the research published in Scientific Reports.
The ancient climate was likely subtropical, featuring forests alongside savanna-like and shrubland habitats. Nagatitan shared its environment with diverse other dinosaurs, flying reptiles known as pterosaurs, and rivers teeming with crocodiles and fish, including freshwater sharks.
Despite the presence of predators, Nagatitan’s immense size offered significant protection. The ecosystem’s largest carnivore, a relative of the giant African meat-eating dinosaur Carcharodontosaurus, was likely around 26 feet (8 meters) long and weighed about 3.5 tons.
“At that size, it was dwarfed by Nagatitan. At full size, Nagatitan likely had very little to fear in terms of predation,” Sethapanichsakul noted.
Predators typically avoided healthy adult sauropods due to the risk of being crushed, instead targeting the old, sick, or vulnerable young.
“Indeed, sauropods are known to have grown very quickly after hatching, and this probably relates to the dangers of predation. The sooner sauropods could become large, the safer they were because they would have been more difficult to tackle,” added University College London paleontologist and study co-author Paul Upchurch.
Sauropods include the largest land animals in Earth’s history. While Nagatitan was undeniably huge, it did not reach the colossal scale of some South American sauropods like Argentinosaurus and Patagotitan, which exceeded 100 feet (30 meters) in length. The dinosaur’s name, Nagatitan, references Naga, a serpent-like being prominent in Asian religious traditions and depicted in various Thai temples.
Thailand is now known to have 14 named dinosaur species.
The inclusion of “titan” in its name is fitting, as Sethapanichsakul suggests Nagatitan could be considered Southeast Asia’s last “titan.” The region later transformed into a shallow sea during the Cretaceous period, preventing further sauropod habitation. Nagatitan offers crucial insights into sauropod diversity in the region, being the largest and geologically youngest known from Southeast Asia.
It belonged to a subgroup of sauropods characterized by bones with numerous internal air sacs and thin walls, which lightened their skeletons. This group emerged around 140 million years ago, achieved global distribution, and by 90 million years ago, became the sole surviving sauropod lineage worldwide, thriving until the dinosaur age concluded 66 million years ago with an asteroid impact.
Nagatitan lived during a period of rising atmospheric carbon dioxide levels and high global temperatures. “Sauropods seem to have become particularly large at this time, with gigantic forms living in South America, China, probably North Africa, and now with Nagatitan a fairly large one in Southeast Asia,” Upchurch explained.
“This possible relationship between large body size and high climatic temperatures is not fully understood, but it’s likely that the high temperatures had an impact on the plant fodder that was important to sauropods, which were very large-bodied herbivores. Nagatitan gives a glimpse of the period leading up to the eventual peak in body size and temperatures about 10 to 15 million years later.”
