Every bone has stories to tell. Some, such as size or the animal’s place in the evolutionary tree, you scrape off the surface. But others remain hidden until you cut inside.

Thanks to more than 30 years of fieldwork, Montana’s Museum of the Rockies has amassed a huge collection of Maiasaura bones. From the number of right-side tibiae – the larger of the two bones that make up the lower leg – they’ve been able to count at least 32 individual dinosaurs at the one site. (The sample probably contains a higher number, but 32 is the absolute minimum.) Most of these limb bones appear to be healthy, but, when MOR researchers cut into them, two of the tibiae showed signs