Tyrannosaurus Rex may have been fierce, but it was vulnerable to a parasite found commonly in today's birds. Evidence released yesterday shows these dinosaurs shared more than a common genetic ancestor with birds. They also died of the same infections.
In a paper published yesterday on PLoS One, a group of international researchers described how they examined the fossils of several T-Rex specimens, and found ten separate individuals who showed signs of trichomonosis - a parasitic infection that eats through the jawbones of birds. The parasites cause lesions on the throat and lower jaw in birds, eventually eating into the bones. Birds of prey are particularly vulnerable to trichomonosis. But birds also possess a unique form of white blood cell called heterophil that isolates infections like trichomonosis to one region of the body and prevents them from spreading. So the birds don't actually die from the disease - instead, they starve to death because so much of their jaws and throats are eaten away that they can no longer swallow.
You can see the telltale lower jaw bone holes caused by trichomonosis in these T-Rex fossils. The researchers speculate that many dinosaurs died of the disease, and that T-Rex probably spread it during fights when they commonly bit each other on the head. Cannibalism is another possible way they spread the disease (birds today often get it from eating infected pigeons).
Paleontologist Ewan Wolff, who contributed to the paper, said:
The holes in tyrannosaur jaws occur in exactly the same place as in modern birds with trichomonosis. The shape of the holes and the way that they merge into the surrounding bone is very similar in both animals. The cause of these holes in tyrannosaurs has previously been attributed to tooth gouges from biting or bacterial infections, but we think a trichomonosis-type disease is much more likely given the position and nature of the holes.
Added his fellow researcher Steven Salisbury:
It's ironic to think that an animal as mighty as [T-Rex fossil] ‘Sue' probably died as a result of a parasitic infection. I'll never look at a feral pigeon the same way again.
Read the scientific paper via PLoS One