The Tyrannosaurus rex is closer to a chicken than an alligator

A molecular examination confirmed what the scientists believed a long time ago based on the shape of the bones - T. rex, chickens and ostriches shared a common ancestor

Many years ago researchers in the life sciences determined that birds evolved from dinosaurs. They came to this conclusion mainly based on the similarity between the bird skeletons and the dinosaur skeletons, but now this assertion received additional support, from the molecular side.

An examination of collagen proteins extracted from a fossilized femur of a 68-million-year-old Tyrannosaurus Rex confirmed that the T-Rex, chickens, and ostriches share a common ancestor, and to a lesser extent, alligators as well. The bone was discovered in 2003 by paleontologist John Horner of the Museum of the Rockies.

"These results are consistent with predictions made based on the anatomy of the skeleton, thus providing the first molecular proof of the evolutionary relationships of a non-bird dinosaur," says Chris Organ, one of the authors of the paper and a researcher at Harvard University. "Even though we only had six proteins - a total of 89 amino acids - from the T-Rex, we were able to maintain these relationships."

"Examinations of the peptide sequence in the T-rex fossil bones confirmed that the new methods of molecular systematics agree with the traditional taxonomic classification, based on morphology or shape," says Paul Filmer, Director of the Department of Earth Sciences at the National Science Institute who funded the study.

The second author of the paper, Marie Schweitzer of the University of North Carolina and the North Carolina Museum of Natural Sciences, discovered in 2005 that the soft tissue was able to be preserved inside the bone of the T-Rex. The current study is based on a previous study published in Science about a year ago. The previous study was conducted by a group led by John Azara and Lewis Cantley, from the Beth Israel Deacons Medical Center and Harvard Medical School, which for the first time succeeded in extracting and sequencing small pieces of the collagen protein from the T-Rex.

Azara became involved in collagen protein analysis due to his expertise in mass spectrometry methods, capable of sequencing minute amounts of proteins extracted from human tumors.

In the current study Organ, Azara and their colleagues compared collagen proteins from 21 species living today. Their goal was to find T-Rex's place in the family tree of the animal kingdom, by using molecular evidence.

"Most of the collagen sequence was obtained from protein and genome databases, but we also had to use mass spectrometry to sequence several important organisms, such as the modern alligator and ostrich," says Azara.

"We determined that T-rex was, in fact, closer to birds - to a chicken and an ostrich - than any other organism we tested," he says. "We also showed that it is more closely related to birds than to modern-day reptiles, such as alligators and green anole lizards."

Although scientists have long suspected that birds are more closely related to dinosaurs than some reptiles, this hypothesis has been based for years mainly on the morphological similarity between the skeletons of birds and dinosaurs.

Another conclusion from the study was reached through the analysis of collagen protein sequences 160,000 to 600,000 years old, extracted from mastadon bone (ancient elephant). The analysis proved that there is a close phylogenetic relationship between the extinct mastodons and modern elephants.

For information on the website of the National Science Foundation in the USA