Soft, organic material discovered inside a Tyrannosaurus rex fossil that scientists believed was 70 million-year-old dinosaur tissue may have been nothing more than ordinary slime, scientists said in a study published Wednesday.
Researchers reported in the online journal PLoS ONE that bacterial colonies infiltrating tiny cavities in the bones long after the dinosaurs died may have naturally molded into shapes resembling the tissues they replaced.
Carbon dating on one sample showed the tissue-like material was modern, circa 1960.
After further examination with light and electron microscopy, researchers concluded the substances were most likely remnants of biofilms, or layers of bacterial cells and the molecules they secrete.
The finding sparked a strong response from the initial researchers. Mary Schweitzer, the biologist from North Carolina State University who found the original T. rex tissue, said that errors in the current study “seem to underlie a fundamental misunderstanding of our work, our data and our interpretations.”
The dinosaur tissue was reported in 2005 after Schweitzer’s team, working at a remote dig site in Montana, was forced to break a T. rex femur into chunks small enough to be transported by helicopter. Inside were pieces of rubbery material that looked like blood vessels and bone marrow.
Hoping to find more samples, a team at the Burke Museum of Natural History and Culture at the University of Washington decided to examine a fossilized turtle toe from the museum’s collection.
They were astonished to see small spheres reminiscent of blood cells, much like those reported by Schweitzer’s group.
They dissolved the bone in mild acid, exposing tissue that resembled vessels and bone-forming cells, findings similar to what Schweitzer’s group had reported.
But as they examined more fossils, Thomas Kaye, an associate researcher at the museum and the leader of the group, was puzzled that he found similar materials in nearly every bone. It didn’t make sense that so much tissue could have survived millions of years.
The solution came from Zbigniew Sawlowicz of Jagiellonian University in Poland, who identified the spheres as framboids, iron-containing structures known to form in the presence of bacteria.
Examination revealed pockets of microbe-like shapes and tiny furrows that may have been trails bacteria blazed through the muck, the researchers said.
Kaye said the evidence – and common sense – clearly pointed to bacterial leftovers. “Believe me, I didn’t want it to be this explanation,” he said. “I would much rather have it be dinosaurian tissue.”