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| Nagatitan chaiyaphumensis Sethapanichsakul, Khansubha, Manitkoon, Hanta, Mannion & Upchurch, 2026 นาคาไททัน ชัยภูมิเอนซิส || DOI: doi.org/10.1038/s41598-026-47482-x Artwork by facebook.com/DinoThaiThai |
Abstract
Sauropod dinosaur remains comprise the majority of the Mesozoic vertebrate fossil record in Thailand. However, they are rare and fragmentary in the Aptian–Albian (Lower Cretaceous) Khok Kruat Formation, the stratigraphically youngest fossil-bearing Mesozoic Thai stratigraphic unit. Based on a partial postcranial skeleton, we present the first diagnostic sauropod specimen from this formation, which represents a new somphospondylan titanosauriform, Nagatitan chaiyaphumensis n. gen. n. sp. Nagatitan is diagnosed by two autapomorphies and a unique character combination, including the presence of two distinct hyposphene-hypantrum morphologies within the middle–posterior dorsal vertebrae. Phylogenetic analyses under maximum parsimony, using a data matrix containing 153 taxa and 570 characters, produce well-resolved topologies that place Nagatitan within the somphospondylan clade Euhelopodidae. Nagatitan does not form an endemic subclade with the approximately contemporaneous Southeast Asian euhelopodids Phuwiangosaurus and Tangvayosaurus, with a suite of anatomical features distinguishing these taxa. We estimate a body mass of 25–28 tonnes for Nagatitan, and suggest it was part of a broader middle Cretaceous body size increase in Asian titanosauriforms, facilitated by rising temperatures and expanded suitable habitat. The discovery of Nagatitan expands the known diversity of Southeast Asian sauropods and improves our understanding of titanosauriform biogeography within the region.
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| Schematic representation of the skeleton of Nagatitan chaiyaphumensis gen. et. sp. nov. Preserved bones are highlighted. Scale bar equals 1 m. |
Systematic palaeontology
Dinosauria Owen, 1842
Saurischia Seeley, 1887
Sauropoda Marsh, 1878
Titanosauriformes Salgado, Coria & Calvo, 1997
Somphospondyli Wilson & Sereno, 1998
Euhelopodidae Romer, 1956 (sensu D’Emic, 2012)
Nagatitan chaiyaphumensis gen. et sp. nov.
นาคาไททัน ชัยภูมิเอนซิส
Holotype: SM2025-1-546 to SM2025-1-556—four dorsal vertebrae, five dorsal ribs, four sacral vertebrae, five sacral ribs, right humerus, right ilium, left and right pubis, mostly complete right femur.
Diagnosis: Nagatitan can be diagnosed by a unique combination of characters (autapomorphies denoted with an asterisk): (1) paired postzygapophyseal centrodiapophyseal fossa present on posterior dorsal neural arches; (2*) hyposphene of middle dorsal vertebrae exhibits a triangular morphology, becoming a vertical ridge in posterior dorsal vertebrae; (3) parapophysis positioned dorsal to the prezygapophysis on posterior dorsal neural arches; (4) spinopostzygapophyseal laminae of middle and posterior dorsal neural spines divided into lateral and medial branches throughout their length; (5) bifurcated middle dorsal neural spines; (6*) triangular anterior aliform processes present on posterior dorsal neural spines; (7) prominent bulge on posterolateral margin of humerus, approximately level with the deltopectoral crest, that interrupts the lateral humeral margin in anterior view; (8) rounded proximolateral corner of humerus; (9) humeral shaft exhibits a high eccentricity value (> 2.5); (10) distal end of the pubis transversely expanded along the lateral surface relative to the shaft; and (11) proximal third of femur with anteroposteriorly narrowed lateral margin forming a flange-like trochanteric shelf and a medially bounding vertical ridge along the posterior surface.
Locality and Horizon: Ban Pha Nang Sua, Nong Bua Rawe District, Chaiyaphum Province, Thailand; Khok Kruat Formation, Aptian–Albian, upper Lower Cretaceous.
Etymology: The generic name is derived from Naga, referring to the mythological serpent-like creature found in various Asian cultures, especially in northeastern Thailand, often associated with water and Buddhism, and titan, a giant in Greek mythology. The specific epithet is derived from the province of Chaiyaphum, Thailand.
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3D skeletal reconstruction by Matus Charoenjit |
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| Stylized life reconstruction of Nagatitan chaiyaphumensis gen. et. sp. nov. within the arid floodplains of late Early Cretaceous Aptian–Albian Thailand Artistic reconstruction by Patchanop Boonsai (Draconos Takeji) |
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| Non-sauropod faunal remains discovered in the Ban Pha Nang Sua locality: (a) Allosauroid tooth (SDM2025-1-562) in labial view, (b) spinosaurid tooth (SDM2025-1-561) in labial view, (c) crocodyliform tooth (specimen lost during the excavation) in lingual view, (d) Heteroptychodus steinmanni tooth (SDM2025-1-563) in apical view, and (e) mold of cf. Yunnanoconcha sp. (SDM2025-1-560) in external view. (f) Stylized illustration displaying the vertebrate fauna assemblage known from the Khok Kruat Formation modified from Manitkoon et al. 2023. Shaded black silhouette indicate tentative taxa. Nagatitan chaiyaphumensis gen. et sp. nov. shaded in blue. Scale bars equal 10 mm. |
Thitiwoot Sethapanichsakul, Sasa-On Khansubha, Sita Manitkoon, Rattanaphorn Hanta, Philip D. Mannion and Paul Upchurch. 2026. The First Sauropod Dinosaur from the Lower Cretaceous Khok Kruat Formation of Thailand enriches the Diversity of somphospondylan titanosauriforms in Southeast Asia. Scientific Reports. 16; 12467. DOI: doi.org/10.1038/s41598-026-47482-x [14 May 2026]
