Describer

Buffetaut, Suteethorn & Tong, 1996

Time

Cretaceous Early Barremian

Classification

Saurischia Theropoda Tyrannosauria Tyrannosauridae

Diet

Carnivore

Fossilsite

Sao Khua Formation, Isan region, Thailand

Length

6.5 meter

Info

Genus - Typespecies

The material recovered includes a pelvis and a number of back and tail vertebrae. The name honors the area where it was found, the Isan region of Thailand, once called Siam, and also indicates its taxonomic placement as the oldest and one of the most primitive tyrannosaurids ever found, an early ancestor of such later beasts as Tarbosaurus and Tyrannosaurus rex . Identification as a tyrannosaurid based on some distinctive features of the pelvis and vertebrae. However, there seems to be some dispute over whether the identification of the new animal as a tyrannosaur is valid. Another early tyrannosaur is Eotyrannus from the Wessex Formation, Isle of Wight, England

Paul Sereno doesn\\\'t think it\\\'s a tyrannosaur because the known material doesn\\\'t show all the right features for a tyrannosaur. Mark Norell of the AMNH agrees, and also says that the discoverers should not have named the animal yet. While he says it\\\'s an important find, he believes the material is not complete enough for a full, formal description.

Thomas Holtz, vertebrate paleontologist for U. Maryland, both agrees and disagrees with Sereno. Holtz\\\'s doctorate was on tyrannosaur origins. He sees the new animal as being similar to tyrannosaurs, close enough that it could represent a tyrannosaur ancestor.

The discoverers, led by Eric Buffetaut of the Centre National de la Recherche Scientifique in Paris, are defending their find as the oldest and most primitive known tyrannosaurid, ancestral to all the later ones.

Sues considers the currently available material of Siamotyrannus isanensis insufficient for even establishing the dinosaurian status of this taxon.

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