More than 30 specimens of "Tyrannosaurus rex" have been found. Some of them are nearly complete skeletons, and soft tissue and proteins have been reported in at least one of these specimens. Research is done on its biology, life history and biomechanics. The feeding habits, physiology and potential speed of "Tyrannosaurus rex" are some topics. Some scientists think "Tarbosaurus bataar" from Asia is a second species of "Tyrannosaurus", but others think "Tarbosaurus" is a separate genus.