Sue is thought to be one of the best preserved Tyrannosaurus rex specimens ever unearthed—and that stellar preservation extends to the eight holes in her jawbone. Those holes have long been a mystery, and the upshot of a new study published in Cretaceous Research is that they remain a mystery, though one leading theory has been ruled out. Reuters reports the holes—some with a diameter akin to a golf ball's—appear on the rear of Sue's left lower jawbone. Study co-author Jingmai O'Connor of Chicago's Field Museum explains what makes the mystery so "weird": The holes are large but didn't manage to kill the T. rex and had started to heal.
And Sue isn't alone. As the study notes, "Many tyrannosaurid specimens preserve unusual pathologies in the caudal half of the mandible that are of uncertain origin." Experts had suggested a microbial infection was the cause of these holes, but lead study author Bruce Rothschild of the Carnegie Museum of Natural History determined that wasn't the case. The microbes that were suspect are protozoans, and one widespread protozoan disease found in birds is called trichomoniasis. O'Connor explains in a press release that "for this study, we wanted to compare the damage in Sue's jaw with Trichomonas damage in other animals to see if the hypothesis fit."
The skeleton of a bird with a history of trichomoniasis was located in the Field Museum's collection, and O'Connor says the signs of infection manifested differently. In the bird "they are in the back of the throat, but there aren't holes bored through the jaw." Rothschild suggested perhaps it was claw-inflicted damage sustained during mating, but O'Connor waves that theory off. "They're just random, all over the place," she notes of the holes. She says there are still other theories to explore, telling Reuters, "It's a good paleontology mystery—my favorite." (More discoveries stories.)
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