In 1988, a "Tyrannosaurus rex" known as "Devil Rex" (MOR 555) was unearthed in the Russell National Wildlife Refuge. The specimen skeleton was approximately 46 percent complete and included the first complete "T. rex" forelimb. Doctoral candidate Mary Schweitzer found heme, a biological form of iron that makes up hemoglobin (the red pigment in blood), within some bones of the fossil. The fossil is now the centerpiece of the renovation dinosaur hall at the National Museum of Natural History in Washington, D.C.