Siamosaurus (meaning "Siamese lizard") is a genus of spinosaur dinosaur. from early Creataceous Thailand. The size of the animal is unknown, but it may have reached a length of about 9.1 meters (30 ft). The type species, Siamosaurus suteethorni, was formally described by Buffetaut and Ingavat in 1986. There is very little information on this Cretaceous meat-eater, but it is known from teeth that closely resemble those of Spinosaurus it may have eaten fish.

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