If she’d been male, we’d probably have heard all about it a lot sooner. But it seems that Sue – the tyrannosaurus in the Field Museum of Chicago – was killed not by a bite but by a throat infection, in a discovery that may help explain why the rest of her species died out.
A study led by researchers at the University of Queensland pins the demise of Sue and nine other tyrannosaurs with similar scars on an avian parasitic infection called trichomonosis. This is caused by a single-celled parasite that causes similar lesions on the mandibles of modern birds, raptors in particular.
The infection in Sue’s throat and mouth may have been so acute that the 42-foot-long, seven-ton dinosaur starved to death.
The lesions were previously attributed to bite wounds or, possibly, 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,” explains Wolff.
Tyrannosaurs frequently bear the scars of battle. But while bite marks are often messy, scarring and puncturing bone, the holes caused by trichomonosis tend to be neat and have relatively smooth edges.
Transmission of the parasite may have been through salivary contact or cannibalism, says Wolff, noting that there is no known evidence of trichomonosis in other dinosaurs.
For the disease to show up so clearly, it would have had to be at a pretty advanced stage, as the parasite is typically found as a film in the back of the throat.
“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.”
Details are in Public Library of Science One.