Did a tiny parasite kill the Field Museum's giant Tyrannosaurus Sue?

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An artist's rendering of a T-rex suffering from a trichomonosis-like disease, a parasitic infection caused by a protozoan, a single-celled organism that infects the mouth and throat and may have caused the animal to starve to death, according to a study conducted by an international team of researchers. The renderings show the infection and how it relates to the lesions found on the mandible of 'Peck's Rex' (Museum of the Rockies). Renderings by Chris Glen, University of Queensland

When you look at the massive skeleton of Tyrannosaurus Sue, the famed T-Rex at the Field Museum, it's hard to figure out what could kill this massive beast - the top of the Cretaceous food chain roughly 100 million years ago.

Could it have been after mortal combat with another T-rex? Sue is the largest complete skeleton of her kind, but hardly the largest T-rex, a species thought to have been mighty feisty and even carnivorous. Could it have been a natural disaster - we're not talking an asteroid, but simply an earthquake, lighting, a flood or the like? What about starvation? It takes a lot of critter kibble to keep a 7-ton meat-eater marauding the plains of Earth.

Or did Sue simply need a good ear, nose and throat doctor - one who specializes in birds?

That's the theory put out in a new study spearheaded out of the University of Wisconsin-Madison and published in the online journal Public Library of Science One. The team, headed by Ewan D.S. Wolff of the University of Wisconsin-Madison and Steven W. Salisbury of the University of Queensland, Australia, believes the massive beast was felled by a mini parasite common today in birds.

wolff.jpegWolff, right, a vertebrate paleontologist and a third-year student at the UW-Madison School of Veterinary Medicine, theorizes in the report that the 42-foot-long Sue may have suffered from trichomonosis, a nasty parasite that attacks the jaws of birds - particularly raptors - and can become serious enough that is causes starvation due to deterioration of the back of the jaw and throat.

"What drew my attention to trichomonosis as a potential candidate for these mysterious lesions on the jaws of tyrannosaurs is the manifestation of the effects of the disease in [bird] raptors," explains Wolff. "When we started looking at trichomonosis in greater depth, there was a story that matched some lines of evidence for transmission of the disease in tyrannosaurs."

According to the report, the parasite can be carried in food sources, like pigeons, that predator birds, like hawks, eat. While the prey remains unaffected, the predators can suffer and pass along ill affects:

In birds, trichomonosis is caused by a protozoan parasite called Trichomonas gallinae. It can be transmitted from birds such as pigeons, which commonly carry the parasite but often suffer few ill effects, to raptors such as falcons and hawks, where it causes serious lesions in the mandibles.

Wolff and his research team conclude that Sue - and a group of nine other Tyrannosaur skulls studied - exhibits lesions and degeneration consistent with the parasitical infection. But still, would it be enough to eventually kill an beast the size and power of an adult Tyrannosaur?

"The lesions we observe on Sue suggest a very advanced stage of the disease and may even have been the cause of her demise," says Wolff. "It is a distinct possibility as it would have made feeding incredibly difficult. You have to have a viable pharynx. Without that, you won't make it for very long, no matter how powerful you are."

Sometimes, it seems, it's not the bigger fish to be feared, but the unseen that can be an undoing.


Sue, the largest and most complete Tyrannosaurus rex skeleton ever found, is shown at the Field Museum of Natural History May 17, 2000, in Chicago. (AP)

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    This page contains a single entry by Craig Newman published on September 29, 2009 11:20 AM.

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