Bones tell life stories of living and extinct creatures

As a practicing rheumatologist, Bruce Rothschild, M.D., studied maladies in the bones of living humans. In the 1980s, he began to study bones in the fossil record, too.

Rothschild, a KU Biodiversity Institute research affiliate scientist, looks at the fossil record for stress fractures, broken bones and scars. This evidence of activity is found in the bones of modern humans as well as those of extinct animals. Diseases, too, manifest in bones: syphilis leaves scars and deforms bones, for example, and tuberculosis causes bone lesions. Rothschild uses these clues to figure out an animal’s diseases, past injuries and even posture, and draws further conclusions about its lifestyle, such as hunting, eating and mating habits. The tricky part is that injuries and diseases manifest themselves in different ways in each individual. "You have a spectrum of disease, so you must have a spectrum of animals to study," Rothschild said. "Put it all together and you get a pattern, and it’s the pattern that is most informative." To establish that pattern, Rothschild must study every bone of a family or species that he can find. "If I look at one diseased bone, I can make some guesses at its diagnosis, but I’m not going to be able to diagnose it with 100 percent confidence," he said. "One has to have large numbers to be able to answer the question, ‘Is this what we see in the general population?’" The KU collections have been important to Rothschild because they’re so extensive; KU has the largest collection of mosasaurs in the country. By studying mosasaur bones, Rothschild was able to determine that Cretaceous animals got "the bends," or decompression sickness. Decompression sickness can occur as a result of rapid changes in pressure when a living thing rises too quickly from a deep dive. Rothschild made the discovery when comparing two kinds of vertebrae – fused vertebrae that showed signs of disease versus vertebrae that appeared normal. A cross-section analysis of the fused vertebrae showed what he anticipated; there were signs of disease. However, a cross-section of the normal vertebrae selected for comparison revealed bands of dead bone, a condition called avascular necrosis. The bands of bone were characteristic of decompression syndrome. Rothschild concluded that some mosasaurs were deep divers, a suggestion first made in 1800, and, thanks to the diversity of specimens in KU’s collection, helped identify which types of mosasaurs were likely to have that behavior.