Named By: E. Buffetaut, V. Suteethorn & H. Tong - 1996.
Classification: Chordata, Reptilia, Dinosauria, Saurischia, Carnosauria, Metriacanthosauridae, Metriacanthosaurinae.
Species: S. isanensis (type).
Size: Roughly about 6 to 7 meters long.
Known locations: Thailand - Sao Khua Formation.
Time period: Berriasian-Barremian of the Cretaceous.
Fossil representation: Originally based upon a hip as well as some sacral (hip) and caudal (tail) vertebrae. A femur and teeth have now also been referred to the genus.
named in 1996, Siamotyrannus was originally
thought to represent
one of the earliest known occurrences of a large tyrannosaur,
hence the name Siamotyrannus which combines the
old name for
Thailand, Siam, with the ancient Greek for tyrant. However later
studies of Siamotyrannus have come to the
Siamotyrannus was not a tyrannosaur but another kind
of theropod called
a metriacanthosaurid. Metriacanthosaurids were more primitive
carnosaur theropods, and from these Siamotyrannus
can be further
classified as a metriacanthosaurine similar to genera such as
and of course Metriacanthosaurus.
Going by the holotype fossils, Siamotyrannus would have been a medium sized predatory dinosaur that may have hunted dinosaurs such as the ornithomimosaur Kinnareemimus and the titanosaur Phuwiangosaurus. Siamotyrannus should not be confused with Siamosaurus, a spinosaurid theropod genus so far only based upon teeth found at the same Fossil Bearing Formation as Siamotyrannus.
- The earliest known tyrannosaur from the Lower Cretaceous of Thailand. Nature 381:689-691. - E. Buffetaut, V. Suteethorn & H. Tong - 1996.
- Early Cretaceous dinosaurs from Thailand and their bearing on the early evolution and biogeographical history of some groups of Cretaceous dinosaurs, by E. Buffetaut & V. Suteethorn. In Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History Bulletin 14. p. 205-210, Lucas, Kirkland & Estep (eds). - 1998.