as gharials—which made them well-adapted to catching and feeding on fish. Fossil evidence has shown that besides aquatic prey, spinosaurids also consumed other dinosaurs and pterosaurs. In the Sao Khua Formation, localities such as Wat Sakawan have yielded sauropod remains in association with tooth crowns from Siamosaurus, documenting either predation or scavenging on part of the latter. In 2006, Thai biologist Komsorn Lauprasert examined fossils collected from the Phu Kradung, Sao Khua, and Khok Kruat Formations. In this study, the teeth of Siamosaurus and a Moroccan spinosaurid were compared to those of crocodilians using scanning electron microscopy. Lauprasert found that spinosaurids and crocodilians may have employed similar feeding tactics and been under comparable mechanical constraints, based on resemblances in the microstructure of their tooth enamel. Therefore, Lauprasert suggested that Siamosaurus—as a piscivorous predator—could have replaced the ecological niche of contemporaneous long-snouted crocodilians. He noted that this likely occurred in correlation with the rising aridity of the Sao Khua and Khok Kruat Formations during the Early Cretaceous, since Siamosaurus had better mobility in a dry environment than crocodilians did. This might explain the absence of long-snouted crocodilian fossils from that time and place. Goniopholidid crocodilians were prevalent, however, and since this group had broader, shorter snouts and thus more varied diets, Lauprasert suggested that this would have kept them from competing with Siamosaurus. A similar scenario was proposed for spinosaurids by Hone and colleagues in 2010, who also noted that compared to large crocodilians and obligate aquatic predators, they could more easily travel from one body of water to another in search of prey. Aquatic habits In 2008, French palaeontologist Romain Amiot and colleagues compared the oxygen isotope ratios of remains from theropod and sauropod dinosaurs, crocodilians, turtles, and freshwater fish recovered from eight localities in northeastern Thailand. The study revealed that Siamosaurus teeth had isotope ratios closer to those of crocodilians and freshwater turtles than other theropods, and so it may have had semiaquatic habits similar to these animals, spending much of its daily life near or in water. Discrepancies between the ratios of sauropods, Siamosaurus, and other theropods also indicate these dinosaurs drank from different sources, whether river, pond, or plant water. In 2010, Amiot and colleagues published another oxygen isotope study on turtle, crocodilian, spinosaurid, other theropod remains, this time including fossils from Thailand, China, England, Brazil, Tunisia, and Morocco. The analysis showed that Thai spinosaurid teeth tended