Soft tissue taken from preserved dinosaur bones may not be dinosaur protein at all, but bacteria, paleontologists said on Tuesday.
Dinosaur experts made headlines around the world when they found what appeared to be soft tissue in a broken Tyrannosaurus rex thighbone.
Last April, a team at Harvard University in Massachusetts said they had analyzed a small amount of protein from the sample and shown it had characteristics of living bird and, more distantly, alligators.
But paleontologist Thomas Kaye of the University of Washington in Seattle challenges this idea and says he has seen similar structures and shown them to be bacteria. Specifically, he said, the structures look like bacterial biofilm, a slimy substance that the microbes often form.
"We are not experts in the field," Kaye admitted in a telephone interview. "We are not disagreeing with the fact that their instruments detected protein. We are offering an alternative explanation."
Mary Schweitzer of North Carolina State University had analyzed the material taken from the 68-million-year-old thighbone and found not only what looked like collagen, but structures akin to tiny blood vessels.
Kaye, who looks at ancient material using an electron microscope, said he was trying to duplicate their findings. He said he went to the same formation where Schweitzer's sample came from, dug up a 65-million-year-old dinosaur bone, cracked it open, and looked at it.
Writing in the Public Library of Science journal PloS One, he said he dissolved tissue in acid just as Schweitzer had done.
What had been identified as remnants of blood cells were actually structures called framboids -- microscopic mineral spheres that contain iron," Kaye's team reported.
They tested a variety of other bones, including a turtle's, and found similar structures.
"We determined that these structures were too common to be exceptionally preserved tissue. We realized it couldn't be a one-time exceptional preservation," Kaye said.
He believes what was really inside the T. rex bone was biofilm created by bacteria that grew inside now-disappeared blood vessels and cells.
Schweitzer's team said they had found unusually well preserved tissue and said it was unlikely to have survived in many samples.
