Nagatitan chaiyaphumensis

Nagatitan chaiyaphumensis is the first diagnostic sauropod named from Thailand's Khok Kruat Formation and the largest dinosaur yet described from Southeast Asia. Four back vertebrae, ribs, part of the sacrum and pelvis, a humerus and an almost complete femur document one individual. The describing study recovered it as a euhelopodid somphospondylan, but not as an exclusively Southeast Asian branch with Phuwiangosaurus and Tangvayosaurus. Its immense size is reconstructed from limb-bone dimensions rather than a complete skeleton.

Its fossils occur between approximately 113 and 100.5 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The holotype includes four dorsal vertebrae with changing accessory joint shapes along the back, five dorsal ribs, four sacral vertebrae and associated ribs, a 1.78-metre right humerus, the right ilium, both pubes and a mostly complete right femur reconstructed at roughly 1.9–2 metres. Two unique vertebral features and a distinctive combination of ridges, fossae, limb proportions and pelvic anatomy diagnose the species. Its skull, neck, forefeet, hind feet and tail are unknown.

• Two different accessory vertebral-joint morphologies along the middle and rear back
• Bifurcated neural spines on the middle dorsal vertebrae
• Unusually rounded upper outer corner of the humerus
• Very broad, flattened humeral shaft
• Approximately two-metre femur and 1.78-metre humerus

Local resident Thanom Luangnan noticed fossils exposed by low water at the edge of a communal pond near Ban Pha Nang Sua in 2016. Field teams excavated material from 2016 to 2019 and returned in 2024 to recover the remaining bones. Thitiwoot Sethapanichsakul and five colleagues named Nagatitan chaiyaphumensis in May 2026. Naga refers to a serpent-like figure in Asian traditions, especially northeastern Thai culture, titan evokes a giant, and the species name honours Chaiyaphum Province.

Discovery credit: Thanom Luangnan.

Naming authors: Thitiwoot Sethapanichsakul, Sasa-On Khansubha, Sita Manitkoon and 3 coauthors.

The Ban Pha Nang Sua sediments record a meandering river system crossing a semi-arid landscape. Seasonal low water exposed the fossil bed in modern times. Freshwater sharks, bivalves and teeth from spinosaurid and allosauroid theropods occur in nearby layers, although they are not evidence of direct interaction with the Nagatitan individual.

Its column-like limbs and sauropod relationships support four-legged locomotion and high-volume plant feeding. Neck posture, preferred vegetation, group size, migration and reproductive behaviour cannot be tested from the preserved postcranial bones. The Naga-inspired name does not imply an aquatic lifestyle.

• The estimated 27-tonne mass is comparable to about nine adult Asian elephants.
• A local resident found the first bones beside a pond during the 2016 dry season.
• Its right humerus alone is approximately as tall as an adult person.
• It is currently the largest named dinosaur from Southeast Asia.

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1. 01
   The first sauropod dinosaur from the Lower Cretaceous Khok Kruat Formation of Thailand enriches the diversity of somphospondylan titanosauriforms in southeast Asia

   Thitiwoot Sethapanichsakul, Sasa-On Khansubha, Sita Manitkoon and 3 coauthors · Scientific Reports 16 · 2026

   Open source
2. 02
   ‘Last titan’: Southeast Asia’s biggest dinosaur discovered

   University College London · 2026

   Open source