Family history of Mastodon and T. rex

A T. rex femur bone.

Mastodon and Tyrannosaurus rex now have a place on the vertebrate family tree, thanks to a new study.

Back in 2003, researchers an extremely unusual T. rex fossil. Even though most fossils contain only preserved hard tissues, like bones or shells, this one contained some of the dinosaur’s soft tissues, like collagen and blood vessels. You can read more about this discovery here http://www.eurekalert.org/features/kids/2007-04/aaft-nfo040607.php.

Now, Chris Organ of Harvard University and the Museum of Comparative Zoology in Cambridge, Mass and his colleagues have analyzed the proteins in the collagen preserved from that T. rex fossil and another mastodon fossil. They compared these proteins with proteins from 21 modern-day vertebrates, including chickens, ostriches and elephants.

The proteins from T. rex were most similar to those of birds, while those from the mastodon were most similar to elephants.

These results strengthen what researchers had predicted from looking at whole fossils from these animals: that dinosaurs share more of their genetic makeup with birds than with other modern-day vertebrates, and that extinct mastodons and modern-day elephants are also closely related.

These findings suggest that molecular information from long-extinct organisms should be a useful addition to whole fossils for figuring out evolutionary relationships. The study appears in the 25 April issue of the journal Science.

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