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| Southeast Asia map showing the distribution of Jurassic–Cretaceous non-marine sediments in Southeast Asia. in Manitkoon, Deesri, ... et Chanthasit, 2023. DOI: 10.3897/fr.26.e93456 |
Abstract
Ornithischian dinosaurs have been discovered in Thailand, Laos, and Malaysia. These bird-hipped herbivores remain relatively rare by comparison with saurischian dinosaurs. In the Late Jurassic, stegosaurs and basal neornithischians from Thailand showed similarities to Middle-Late Jurassic taxa from China. Ornithischians appeared in the fossil record again during the late Early Cretaceous (Aptian-Albian) of Thailand and Laos. They are represented by non-hadrosaurid iguanodontians and basal ceratopsians. A few specimens have been reported from poorly dated Early Cretaceous rocks of Malaysia. Here, we illustrate the diversity of ornithischian assemblages in Southeast Asia and discuss their palaeobiogeographical implications.
Key Words: Cretaceous, Jurassic, Ornithischia, palaeobiogeography, Southeast Asia
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| Southeast Asia map showing the distribution of Jurassic–Cretaceous non-marine sediments in Southeast Asia (modified from CCOP’s 1:2 million Geologic map of East and Southeast Asia), Number in circles = rock formations: 1, Lower Phu Kradung; 2, Upper Phu Kradung; 3, Phra Wihan; 4, ?Tembling Group; 5, Gagau Group; 6, Khok Kruat; 7, Grès Supérieurs; 8, Xinlong (Thanh and Khuc 2006; Department of Mineral Resources 2014; Uchida et al. 2017; Teng et al. 2019; Yan et al. 2019). |
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| Phylogenetic relationships of non-avian dinosaurs in southeast Asia and southern China. Abbreviations: A, Sauropoda; B, Eusauropoda; C, Neosauropoda; D, Macronaria; E, Titanosauriformes; F, Somphospondyli; G, Tetanurae; H, Allosauroidea; I, Carcharodontosauria; J, Coelurosauria; K, Megaraptora; L, Ornithomimosauria; M, Genasauria; N, Thyreophora; O, Neornithischia; P, Basal neornithischian; Q, Cerapoda; R, Ornithopoda; S, Iguanodontia; T, Ceratopsia (Cuny et al. 2014; Mo et al. 2016; Laojumpon et al. 2017; Chanthasit et al. 2018; Samathi et al. 2019a; Rolando et al. 2022; Sone et al. 2022; Sriwisan et al. 2022). |
Conclusions:
So far, most southeast Asian ornithischian dinosaur fossils have been found in the Khorat Group of north-eastern Thailand. At least six taxa have been reported and dated from the Late Jurassic to the late Early Cretaceous. The oldest are known from the Late Jurassic Phu Kradung Formation represented by stegosaurids and basal neornithischians. There appears to be an absence of ornithischian dinosaurs during the pre-Barremian of the Sao Khua Formation. The Early Cretaceous Khok Kruat Formation (Aptian-Albian) contains abundant advanced iguanodontians plus basal ceratopsians, which reflects the shift from sauropod-dominated to ornithischian-dominated ecosystems. Iguanodontians and psittacosaurids are also found in the Grès Supérieurs Formation of Laos and the Xinlong Formation of southern China with many similarities to the Khok Kruat fauna of Thailand and these formations are considered equivalent in age. The rare dinosaur specimens from Malaysia are also an age anomaly. However, we propose that the ornithischian tooth from the Tembeling Group represents the existence of ornithischians that are missing from the time-equivalent Sao Khua Formation of Thailand. This study illustrates the diversity of ornithischian assemblages in Southeast Asia, providing an updated review and a discussion about their palaeobiogeographic implications.
Sita Manitkoon, Uthumporn Deesri, Prapasiri Warapeang, Thanit Nonsrirach and Phornphen Chanthasit. 2023. Ornithischian Dinosaurs in Southeast Asia: A Review with Palaeobiogeographic Implications. Fossil Record. 26(1): 1-25. DOI: 10.3897/fr.26.e93456
