September 29, 2009

Famous T. Rex May Have Died From Parasite Infection

Sue, the world's most complete Tyrannosaurus rex specimen, which resides in the Field Museum of Chicago, may have been killed by a disease transmitted by parasites, rather than through a bloody battle, scientists reported Tuesday.

The massive reconstructed fossilized remains, known as Sue, possess holes in the jaw, which scientists considered to be wounds from a clash with another dinosaur.

However, scientists have published a new report that shows the 42-foot-long, 7-ton dinosaur may have met her end due to a parasite that still kills many birds today.

Ewan D.S. Wolff of the University of Wisconsin-Madison and Steven W. Salisbury of the University of Queensland, Australia, led a team of researchers in the new study, published in the peer-reviewed online journal PLoS ONE.

Researchers say that Sue and other tyrannosaurs feature similar scars on an avian parasitic infection called trichomonosis, caused by a single-celled parasite that causes similar pathologies on the mandibles of modern birds, raptors in particular.

They claim that Sue may have suffered from the infection in her mouth and throat so much that she starved to death.

"It is a distinct possibility as it would have made feeding incredibly difficult," said Wolff. "You have to have a viable pharynx. Without that, you won't make it for very long, no matter how powerful you are."

Wolff and Salisbury worked alongside co-authors John R. Horner of the Museum of the Rockies, which funded the study, and David J. Varricchio of Montana State University.

They compared lesions on the jaws of Sue and nine other tyrannosaur specimens. In the past, researchers had attributed the scars to either a battle with another dinosaur or a bacterial infection.

"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," Wolff said in a statement.

"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."

The disease infects birds by way of Trichomonas gallinae, a protozoan parasite. Pigeons have been known to carry the disease with little or no life-threatening aspects.

Wolff noted that the pattern and location of lesions in the tyrannosaurs closely matched those exhibited in birds.

He said that the parasite may have been transmitted through the species by way of salivary contact or cannibalism.

"This leads us to suspect that tyrannosaurs might have been the source of the disease and its transmission in its environment," said Wolff.

Image Courtesy The Field Museum


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