Siamotyrannus isanensis Buffetaut, Suteethorn, and Tong 1996:

Buffetaut et al. (1996) considered this fragmentary form from the Barremian Sao Khua Formation of northeastern Thailand to be a primitive tyrannosaurid. It was found here to lie outside Tyrannosauridae proper (aublysodontines and tyrannosaurines), but shares with it the following synapomorphies: 24.1, 25.1.,27.1.,28.1, and3L.1. Instead of the single midline crest on the ilium in tyrannosaurids, however, the Thai taxon has a pair of crests. Siamotyrannus may indeed be an ancestral member of the tyrannosaur lineage, but lacking additional material (in particular, the skull) such a position remains uncertain.