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Primitive ceratopian dinosaurs of the family Psittacosauridae were hitherto known only from central and northern Asia, from northern China to Mongolia and Siberia. This paper reports the discovery of psittacosaurid jaws in Early Cretaceous rocks of the Khorat Plateau in north-eastern Thailand. These fossils are clearly referrable to the genus Psittacosaurus Osborn and may represent a new species. They constitute a significant new element of the hitherto poorly known Cretaceous continental vertebrate fauna of South-East Asia, suggesting that it was basically similar to that of northern and central Asia. This in turn confirms that, contrary to some recent palaeogeographical reconstructions, by Early Cretaceous times the Indochina block, on which the Thai psittacosaurids have been found, had become part of mainland Asia.

The distal part of the fused ischia of a prosauropod from the Nam Phong Formation (late Triassic) of Phetchabun Province, in northeastern Thailand, is described. Comparisons with various prosauropods, as well as with an early sauropod, show that the Thai specimen is especially robust. However, the available material is too incomplete to warrant a precise identification. It is the first vertebrate fossil found in the Nam Phong Formation, the oldest known dinosaur from southeast Asia, and the first prosauropod to be reported from that region.