Fossil backs theory linking dinosaurs to birds Paleontology

Eighty millions years ago, dinosaurs like these hadrosaurs called Brachylophosaurus canadensis roamed what is now Montana. Scientists have discovered blood cells and proteins inside the fossillized femur of one such animal that reveals the close evolutionary links between dinosaurs and their descendants, the modern birds. Courtesy of Julius T. Csotonyi (csotonyi.com); "Leonardo", TM of Great Plains Dinosaur Museum less Eighty millions years ago, dinosaurs like these hadrosaurs called Brachylophosaurus canadensis roamed what is now Montana. Scientists have discovered blood cells and proteins inside the fossillized femur of one ... more Photo: Courtesy Of Julius T. Csotonyi Photo: Courtesy Of Julius T. Csotonyi Image 1 of / 1 Caption Close Fossil backs theory linking dinosaurs to birds 1 / 1 Back to Gallery

Deep inside the single leg bone of an 80-million-year-old duck-billed dinosaur, scientists have found a hoard of proteins and blood cells providing the first clear biochemical evidence that dinosaurs are indeed the ancestors of modern birds - linked by evolution.

Until now those links had been based mainly on physical evidence - on feathers from dinosaur fossils, on their fossil eggs, on their fossilized birdlike nestlings and on the close resemblance of dinosaurs and birds like the famed "flying dinosaur" called archaeopteryx.

Now the same team of scientists, which found similar biological material in a 68-million-year-old Tyrannosaurus rex two years ago and immediately faced indignant challenges from many other researchers, has found striking confirmation in the details of their newest discovery.

The scientists say that the biological material they analyzed in their new study shows the strongest chemical relationship yet with similar bone and blood cells and proteins of two modern bird species - ostriches and chickens.

UC Berkeley paleontologist Kevin Padian, one of the world's leading dinosaur experts, called the new report "extremely important" - even amazing - not only because the techniques that extracted intact tissues like blood cells were so convincing but also because they will enable scientists to study dinosaur evolution as never before.

The report appears in this week's issue of the journal Science.

'Jurassic Park,' T. rex team

Its principal authors are May H. Schweitzer, a paleontologist at North Carolina State University and a longtime dinosaur analyst; Jack Horner, a Montana fossil hunter best known as technical adviser for the movie "Jurassic Park"; and John M. Asara, a Harvard Medical School pathologist.

Schweitzer, Horner and their colleagues first found evidence of soft tissues inside the thigh bone of the T. rex two years ago, a finding that surprised scientists who did not believe such fragile material could last so long without degrading completely.

A year later, Schweitzer and Asara reported in Science that molecular analysis of the T. rex bones showed a tentative relationship to modern birds - but not to reptiles like alligators - and the challenges erupted. Some scientists insisted that the material had come from later contamination, others claimed that the analysis was deeply flawed, and still others maintained their strong belief that dinosaurs were the ancestors of reptiles like alligators rather than birds.

If their analysis of the duck-billed dinosaur holds up after more testing - using mass spectrometry and scanning electron microscopy - Schweitzer and her team will be vindicated.

An article accompanying the report in Science quotes mass spectrometry expert Matthew Collins of the University of York in Britain as saying that "that would transform the way we do paleontology" by turning the study of prehistoric life into a scientific discipline much like genetics and molecular biology.

Although no one expects that fragile DNA in the genes of such ancient animals as dinosaurs could ever be recovered, tracking amino acids in the proteins of the Schweitzer team's dinosaur could yield excellent insights for evolutionary studies of the entire dinosaur tribe. Dinosaurs grew more and more diverse from their origins some 248 million years ago until they all went extinct about 65 million years ago - with only birds left to carry on their lineage.

Horner, a paleontologist at the Museum of the Rockies, excavated the fossil femur of the dinosaur's hind leg two years ago. It was a hadrosaur named Brachylophosaurus canadensis, and the single bone had lain "untouched and protected" under 23 feet of hard sandstone, Schweitzer's team said.

Protecting fossil

To protect it, Schweitzer's team members carefully jacketed their femur in five inches of sandstone before exposing their find to the air to begin their study. They plucked each bone and sediment sample from the jacket with sterile instruments, wrapped them in layers of foil and placed them in sealed jars to be distributed to the separate laboratories that would perform the independent analyses, Schweitzer said.

"As with everything Mary Schweitzer does, it's incredibly careful and tested six ways to Sunday," said Padian, who was not part of the team. "Getting this kind of preservation in another kind of dinosaur (besides T. rex) is really amazing. The collagen fibers, the molecular analysis that establishes these tissues as closest to T. rex and birds, this would have been unthinkable just a few years ago."