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Temporal range: Early Cretaceous
An artist's restoration of Siamosaurus suteethorni
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Superfamily: †Megalosauroidea
Family: †Spinosauridae
Genus: Siamosaurus
Buffetaut & Ingavat, 1986[1]
Binomial name
Siamosaurus suteethorni
Buffetaut & Ingavat, 1986 [1]

Siamosaurus, meaning "Siamese lizard", (SIE-ah-moe-SORE-us) is an extinct genus of spinosaurid which existed during the early Cretaceous period, Thailand. The exact size of this dinosaur is currently unknown, however most estimates suggest that it was around 9.1 metres (30 ft) in length and 2-3 tons in weight.

Little is known about Siamosaurus. Its teeth closely resembled those of its relative species; like Spinosaurus aegypticus, its diet is presumed to be mainly consisted of aquatic animals; like large fish & crocodymorphs; albeit it is known that the spinosaurids were generalist carnivores; indicating siasmosaurus would be able to hunt/search for the terrestrial prey as well. This carnivore generalism seems to be the case as some of the siasmosaurus remains found to be with the direct assosication with sauropod remains [2]

Habitat and behavior

According to a 2010 publication by Roman Amiot and his colleagues found that oxygen isotope ratios in spinosaurid remains suggest semiaquatic lifestyles. Further comparisons between spinosaurid teeth and those of a contemporary theropod, crocodile and turtle showed that they were more similar to those of crocodilians and turtles than was originally believed, further supporting the notion that Siamosaurus and some species of spinosaurids were likely semi-aquatic. Siamosaurus specimens tend to have the largest difference to theropods and Spinosaurus had the smallest. The results of the tests concluded that some spinosaurids had lifestyles similar to crocodilians and hippopotamuses and spent most of their daily life in water.

Its semiaquatic life also suggests that Siamosaurus was able to live alongside other theropods without competing for food, since they lived in different habitats and possessed different diets and ecological niches. This would have however encouraged Siamosaurs to breed more which may or may not have reduced fish populations quite a bit and likely forced the animal onto more terrestrial prey items.

Siamosaurus and Ichthyovenator are the only spinosaurs to live in south east Asia. How they got there or why it lived there is unknown. There seems to be no advantage to living there, other than maybe the lack of other spinosaurs and larger carnivores.


  1. 1.0 1.1 Buffetaut, E.; and Ingevat, R. (1986). Unusual theropod dinosaur teeth from the Upper Jurassic of Phu Wiang, northeastern Thailand. Rev. Paleobiol. 5: 217-220.
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