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

The most abundant and most diverse dinosaur remains hitherto found in Thail and come from the Sao Khua Formation, now considered pre-Aptian, Early Cret aceous in age. This assemblage includes theropods (the early and primitive tyrannosaurid Siamotyrannus isanensis; an early but relatively advanced orn ithomimosaur; the enigmatic Siamosaurus suteethorni, and possibly another, very small theropod) and sauropods (Phuwiangosaurus sirindhornae and anothe r, poorly known taxon). The Sao Khua fauna, which includes neither Psittaco saurus nor iguanodontids, seems to be older than any of the vertebrate asse mblages from the Gobi Basin. Several of the dinosaurs from the Sao Khua For mation may be close to the origin of groups that later played an important part in the dinosaur faunas of Asia ('nemegtosaurid' sauropods) or both Asi a and North America (tyrannosaurids, ornithomimids). (C) 1999 Elsevier Scie nce B.V. All rights reserved.