Temporal range: Early Cretaceous
An artist's restoration of Siamotyrannus isanensis
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Unranked: Carnosauria
Superfamily: Allosauroidea
Family: Metriacanthosauridae
Subfamily: Metriacanthosaurinae
Genus: Siamotyrannus
Buffetaut, Suteethorn & Tong, 1996
Binomial name
Siamotyrannus isanensis
Buffetaut, Suteethorn & Tong, 1996

Siamotyrannus, name meaning "Siamese tyrant", is an extinct genus of theropod dinosaur which lived during the early Cretaceous period in what is now Thailand.

Siamotyrannus was a large theropod, with estimates suggests an average length of 7 metres (23 ft) and a weight of around half a ton.[1]


As highlighted by its genus name, Siamotyrannus was originally identified as a tyrannosaur.[2] However, as it lacks some of the fundamental features of a tyrannosaur, its position in the group is not clear.[3] Some scientists refer to Siamotyrannus as a primitive carnosaur, rather than a basal tyrannosauroid, as it possesses several features that occur in some allosaurids and sinraptorids.[4] In 2012, Matthew Carrano e.a. found a position in the Metriacanthosaurinae.[5]



  1. Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 91
  2. Buffetaut, E., Suteethorn, V. and Tong, H. 1996. The earliest known tyrannosaur from the Lower Cretaceous of Thailand. Nature 381: 689-691
  3. Rauhut, Oliver W. M. Special Papers in Palaeontology: The Interrelationships and Evolution of Basal Theropod Dinosaurs (No. 69). The Palaeontological Association: 2003
  4. Holtz, Thomas R. et al. (2004). "Basal Tetanurae." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. p. 101 ISBN 0-520-24209-2
  5. Carrano, M. T.; Benson, R.B.J.; Sampson, S.D., 2012, "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology 10(2): 211–300