The tumor would have encroached upon the cerebellum and brainstem, said Reams, the area of the brain responsible for balance and calculated movement. "Predators, especially, need to be able to make quick decisions and move rapidly," added Larson, who argues that the tumor could explain the juvenile animal's many other injuries.
Perhaps equivalent to an 18-year-old human, the Gorgosaurus may have eventually died from her crippling ailments. Her wounds included a fractured and infected left upper leg bone (femur) with a torn tendon and a shattered left shoulder girdleboth of which had healedin addition to a badly-smashed lower right leg bone (fibula), and pus-filled, infected lower jaws.
Two other pathologies hint at the sex of the specimen. Fused vertebrae at the base of the tail are potentially a "mounting injury" sustained during mating with the larger male of the species. Plus, a loss of bone mass in the tail (like osteoporosis in humans) could be due to the calcium demanded by egg production, added Larson.
Although "a tumor is a distinct possibility, it is by no means a certain diagnosis," commented Elizabeth Rega, an anatomist and expert on fossil pathology at the Western University of Health Science in Pomona, California. Other possible explanations may be that the mass is a mineral concretion in the brain cavity or desiccated brain tissue. Thin, polished sections of the fossil must be examined microscopically to confirm the diagnosis, Rega said.
Rega, who has examined the new specimen, also helped diagnose injuries sustained by "Sue," the world-famous T-rex now on display at the Field Museum in Chicago, Illinois. "A mass such as this in a living animal would be suggestive of tumor, but there are other concerns with distorted and fossilized animals," she said.
Bruce Rothschild, a radiologist and director of the Arthritis Center of Northeast Ohio in Youngstown, disagreed. "It certainly would take a bizarre [fossilization] event to have created this appearance," he said. "The position and character may well be a tumor, but it still needs to be proven that this is not simply broken skull fragments that 'fell in.'"
Nevertheless, "this is an amazing specimen," commented Rothschild, who has helped in the diagnosis of previous Black Hills Institute specimens.
Rothschild's own research, the first wide survey of cancer in dinosaurs, was published in the November edition of the German science journal Naturwissenschaften. His team x-rayed the bones of hundreds of dinosaurs in museums across the United States. They found 29 tumorsall in hadrosaurs, a particularly cancer-prone group of duck-billed dinosaur.
SOURCES AND RELATED WEB SITES