How ‘skin bones’ helped large dinosaurs survive

In studying dinosaurs, paleontologists have found that bones contained entirely within the skin of some of the largest dinosaurs on Earth might have stored vital minerals to help the massive creatures survive and bear their young in tough times, according to new research.

University of Guelph biomedical scientist Matthew Vickaryous co-authored a paper published in Nature Communications on November 29 about two sauropod dinosaurs – an adult and a juvenile – from Madagascar.

The study suggests that these long-necked plant-eaters used hollow “skin bones” called osteoderms to store minerals needed to maintain their huge skeletons and to lay large egg clutches. In addition, sediments around the fossils show that the dinosaurs’ environment was highly seasonal and semi-arid, with periodic droughts causing massive die-offs. Vickaryous said:

Our findings suggest that osteoderms provided an internal source of calcium and phosphorus when environmental and physiological conditions were stressful.

What are osteoderms in dinosaurs?

The osteoderms appear like footballs sliced lengthwise and are about the size of a gym bag in the adult. And these bones are the largest osteoderms ever identified. Interestingly, extensive bone remodelling probably caused the adult’s osteoderm to be hollow, said Vickaryous.

Armoured dinosaurs often had osteoderms. For instance, stegosaurs had bony back plates and tail spikes, and ankylosaurs sported heavily armoured bodies and bony tail clubs. Besides dinosaurs, today these “skin bones” appear in such animals as alligators and armadillos.

Such bones were rare among sauropod dinosaurs and appear only in titanosaurs. These massive plant-eaters included the largest-ever land animals.

Other studies have shown that female titanosaurs laid dozens of volleyball-sized eggs. Modern crocodiles and alligators also lay clutches of dozens of eggs and are known to reabsorb minerals from their osteoderms.

Different in adults and juveniles

The researchers found the new osteoderms along with two skeletons of the titanosaur Rapetosaurus. Unlike the hollow adult specimen, the juvenile specimen was solid and showed little evidence of remodelling. That suggests that osteoderms became more important mineral stores as the animals grew, Vickaryous said.

Bottom line: A study published in Nature Communications says that bones contained entirely within the skin of some of the largest dinosaurs on Earth might have stored vital minerals to help the massive creatures survive and bear their young in tough times.

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