Researchers Map Prehistoric Giants' Family Tree, Confirm Dinosaurs Evolutionary Link to Birds

T. rex —> bird relationship derived exclusively from collagen protein sequence data

Protein sequences were obtained from 21 extant and two extinct organisms from public databases and tandem mass spectrometry. Using several phylogenetic algorithms, the non-avian Tyrannosaurus rex dinosaur groups with birds rather than reptiles. These results support evolutionary relationships based on morphology.

[Image © Science]

Analyzing newly discovered soft tissue preserved in a Tyrannosaurus rex femur, a research team publishing in Science has confirmed previous theories suggesting dinosaurs share more of their genetic makeup with birds than with other modern-day vertebrates.

While the evolutionary link between dinosaurs and birds is not new, Chris L. Organ, lead author and a biologist at Harvard University, said his team's new findings are among the first to show that molecular analysis can be used to construct evolutionary histories for extinct species.

The evolutionary link between dinosaurs and birds was originally developed solely by comparing the morphology, or skeletal anatomy, of dinosaur fossils with skeletons of living birds, he wrote.

"Our findings suggest molecular data from long-extinct organisms may have potential for resolving relationships at critical areas of the vertebrate evolutionary tree that have, so far, been intractable," Organ wrote in the Brevia published in the 25 April issue of Science.

By comparing connective tissue proteins from the T. rex femur to that of 21 living organisms, the team confirmed that the king of dinosaurs was more closely related to chickens (Gallus) or ostriches (Struthio), than with green anoles (Anolis) and other reptiles. Based on a similar process, the team also corroborated the close relationship between extinct mastodons (Mammut) and modern-day elephants (Loxodonta).

Organ wrote that his research "bolsters" the use of morphology to hypothesize evolutionary links between living and extinct species because they appear to mirror these new molecular findings.

Brandon Bryn and Benjamin Somers

24 April 2008