A Montana paleontologist and his colleagues believe they have found red blood cells in the fossilized leg bone of a Tyrannosaurus rex and say they have high hopes of extracting DNA from the dinosaur's cells.
The discovery of the putative dinosaur blood cells has not yet been submitted to a scientific journal or independently confirmed but was reported two weeks ago by the National Science Foundation, which has financed the exploratory project.
Jack Horner, a paleontologist at Montana State University who directed the investigation, said in an interview yesterday that his group hoped to find matches between gene fragments left in the preserved blood cells with comparable DNA segments from modern crocodiles or birds.
"If we're lucky enough to find matches," he said, "they could go a long way toward showing what the relationship between dinosaurs and birds might be. We're not there yet, but we think we're getting close."
The femur Mr. Horner's group is studying is part of an unusually well preserved tyrannosaur fossil, more than 65 million years old, which they found and excavated from the Hell Creek Formation in eastern Montana three years ago. The apparent blood cells were discovered by Mary Schweitzer, Mr. Horner's graduate student, who was investigating the histology, or cell structure, of fossilized bone and marrow tissue.
In the past, few paleontologists or molecular biologists believed that biological material could survive for millions of years without becoming mineralized, thus losing its organic molecular structure. The survival of any intact DNA, which ordinarily decays with time, seemed even less likely. But the recent discovery of organic material and even fragments of DNA in ancient plant and animal fossils has changed opinions.
"Two years ago I would have called this baloney," said Dr. Raul J. Cano of California Polytechnic State University at San Luis Obispo, a molecular biologist who has himself extracted DNA fragments from fossilized insects and plants millions of years old.
Told of Mr. Horner's belief that blood cells have survived in a tyrannosaur bone -- and that they may contain dinosaur DNA fragments -- Dr. Cano said: "It's certainly plausible. We have seen similar things ourselves, and there are reports from other investigators of the finding of surviving biological material inside fossil dinosaur bones, especially in the deep bone cortex, which seems to be somewhat protected from mineralization."
Earlier this month Dr. Cano and his associates reported in the British journal Nature that they had extracted DNA from a weevil that had been entombed in amber for 120 million to 135 million years.