Scientists investigating the inner structure of a Tyrannosaurus rex fossil discovered what appeared to be preserved soft tissues, perhaps including intact blood cells, as reported in the March 25, 2005 issue of Science. If confirmed, the unexpected finding could revolutionize our understanding of ancient life forms.

Biological tissues are generally not preserved in the geological record. If conditions are just right, minerals may gradually replace the original specimen over time, resulting in the rare fossil. This mineralization process often erases the finer detail of the original biological structures. The new finding may indicate a previously unknown process by which original biological tissues can be preserved for many millions of years. Researchers will continue studying the specimen retrieved from the Tyrannosaurus rex fossil to determine if it really is the original soft tissue material. Alternatively, researchers may have stumbled upon a “soft” mineralization process by which the fossil retains some of the flexibility and detail of the original specimen, though this seems unlikely.