April 25, 2008
Dinosaurs Closely Related to Chickens
Dinosaurs may have been more closely related to chickens than reptiles, according to a report released on Thursday.
Researchers John Asara and colleagues at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston sought to fill in the gaps of the dinosaurs' family tree.
Molecular analysis, or genetic sequencing, of a 68-million-year-old Tyrannosaurus rex protein from the dinosaur's femur confirms that T. rex shares a common ancestry with chickens, ostriches, and to a lesser extent, alligators, scientists said.
"Last year we just made a very loose connection based on (protein) sequence identification and we had no reptiles," Asara said. "And now with very high probability we can make the connection of T. rex to birds."
The protein was in the form of collagen taken from the fossilized leg of a T. rex that was discovered between Wyoming and Montana in 2003 by paleontologist John Horner of the Museum of the Rockies.
"These results match predictions made from skeletal anatomy, providing the first molecular evidence for the evolutionary relationships of a non-avian dinosaur," co-author Chris Organ, a researcher at Harvard University, said. "Even though we only had six peptides--just 89 amino acids--from T. rex, we were able to establish these relationships."
They weren't able to recover dinosaur DNA, instead they were able to study DNA codes for the proteins.
Before 2005, being able to extract soft tissue from bone was an unobtainable dream, until Mary Schweitzer of North Carolina State University proved it could be done.
She was able to take protein out of a younger mastodon bone.
Scientists said their method of testing ancient preserved proteins can be used in other areas to answer key evolutionary questions, but it also shows that classical methods, based on studying an animal's bones and other physical structures, are accurate.
"Most of the collagen sequence was obtained from protein and genome databases, but we also needed to sequence some critical organisms, including modern alligator and modern ostrich, by mass spectrometry," said Asara.
"We determined that T. rex, in fact, grouped with birds--ostrich and chicken--better than any other organism that we studied," he said. "We also showed that it groups better with birds than modern reptiles, such as alligators and green anole lizards."
On the Net:
North Carolina Museum of Natural Sciences
Beth Israel Deaconess Medical Center
Harvard Medical School
Image Courtesy Wikipedia