Tarbosaurus bataar (Maleev, 1955)

Holtz, TR jr., 2004, Tyrannosauroidea, The Dinosauria, University of California Press, pp. 111-136 : 2

Tarbosaurus bataar , originally referred to Tyrannosaurus (Maleev 1955b) , is based on different ontogenetic stages (Rozhdestvensky 1965; Carr 1999; Currie 2000, 2003a). A partial small tyrannosaurid skeleton from the coeval Subashi Formation in China was once referred to its own genus and species, Shanshanosaurus houyanshanensis Dong, 1977 ; however, reanalysis by Currie and Dong (2001b) reveals that the supposed autapomorphic traits of this taxon (Dong 1977; Paul 1988a; Holtz 2001b) are due to misinterpretation of the anatomy, and this taxon might well represent an extremely young T. bataar . Hurum and Sabath (2003) have reexamined the skull of Tarbosaurus based on new material. Unlike in Tyrannosaurus and other North American tyrannosaurids but as in Alioramus , the nasal lacks a caudally oriented lacrimal process. The caudodorsal process of the maxilla is more massive even than in T. rex . The caudal surangular foramen is reduced compared with those in all other tyrannosaurids. Hurum and Currie (2000) demonstrated that the articulation of the intramandibular joint in Tarbosaurus produced a locking mechanism not seen in other Tyrannosauridae . The forelimb of Tarbosaurus is more reduced than in all other tyrannosauroids (Holtz 2001b; Currie 2003a), with a femurhumerus ratio of greater than 3.5 and a metacarpal I greater than one-half the length of metacarpal II due to the reduction of the latter bone. Thus the general theropod reduction in digital and metacarpal elements from digit V toward digit I (Wagner and Gauthier 1999) is seen in this species more so than in other tyrannosaurids (or indeed than in most nonalvarezsaurid theropods). T. bataar is comparable to Tyrannosaurus rex in size:adults have a skull length of more than 130 cm.