The dinosaur fauna of the Sao Khua Formation of Thailand and the beginning of the Cretaceous radiation of dinosaurs in Asia

The most abundant and most diverse dinosaur remains hitherto found in Thailand come from the Sao Khua Formation, now considered pre-Aptian, Early Cretaceous in age. This assemblage includes theropods (the early and primitive tyrannosaurid Siamotyrannus isanensis; an early but relatively advanced ornithomimosaur; the enigmatic Siamosaurus suteethorni, and possibly another, very small theropod) and sauropods (Phuwiangosaurus sirindhornae and another, poorly known taxon). The Sao Khua fauna, which includes neither Psittacosaurus nor iguanodontids, seems to be older than any of the vertebrate assemblages from the Gobi Basin. Several of the dinosaurs from the Sao Khua Formation may be close to the origin of groups that later played an important part in the dinosaur faunas of Asia (`nemegtosauridʹ sauropods) or both Asia and North America (tyrannosaurids, ornithomimids).