WAS IT . . . OR WASN'T IT?

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TYRANNOSAURUS rex is known only from western North America. However, an extremely close relative, Tarbosaurus bataar, lived in Mongolia at the same time that T. rex terrorized North America. The two mounted skeletons in the picture are a juvenile and an adult Tarbosaurus from the Tsagan-Oola Formation of Mongolia, and are about 70 million years old. These skeletons are in the collection of the Paleontological Institute of the Russian Academy of Sciences in Moscow. In the foreground is a skull of another kind of dinosaur, the hadrosaur ("duckbilled dinosaur") Saurolophus angustifrons, also from the Upper Cretaceous of Mongolia, and a possible food item for Tarbosaurus.

Some paleontologists feel that Tarbosaurus was so closely related to Tyrannosaurus that the two should be placed in the same genus. If this proposal is adopted, then Tarbosaurus will be renamed Tyrannosaurus bataar.