'Dinosaur bends' caused by prolonged diving

August 16, 2012

(Phys.org) -- A recent study identified bone deformities on the fossilized remains of Ichthyosarians, which were giant dolphin-like reptiles that first appeared about 245 million years ago.

The lesions were similar to those human divers develop as a result of changes in body pressure, and suggest the reptiles suffered from a version of ‘the bends’.

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A new analysis by University of Melbourne pathologist Associate Professor John Hayman — published in the latest edition of the Naturwissenschaften: Science of Nature journal — sought to explain what may have caused the bone lesions.

That research argues the scarring may be the result of deep diving and spending too long at depth, causing excess nitrogen to be dissolved in the body, and not from quick ascents as previously thought.

“Ichthyosarians probably evolved the ability to dive deeper and to remain at depth for longer periods,” Professor Hayman said.

“An alternative explanation is that the reptiles developed decompression sickness from being trapped in shallow water by predators.

“It wasn’t from sudden and rapid ascents,” he said.

Associate Professor Hayman said the dangerous practice of deep sea diving wouldn’t have affected the replites’ long-term survival because any ill effects would have developed later in life.

“The wouldn’t have been enough to kill the animal, and wouldn’t have affected it’s ability to hunt or breed.”

Professor Hayman said the new analysis was possible because structure of modern humans’ necks are very similar to the prehistoric .

“The arterial blood supply to the humerus and other bones such as the neck of the femur is highly conserved. It has remained much the same for 250 million years.”

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More information: PDF: visions-download.unimelb.edu.au/Deep-diving%20dinosaurs.pdf

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3.5 / 5 (2) Aug 16, 2012
The article itself does little to explain the difference between the two types of decompression illness - luckily the linked PDF does. One is a result of air in the lungs expanding during quick ascents, and the paper mentions that this happens to untrained divers - trained divers exhale while ascending. I am completely shocked that any scientist would have ever thought this was the type of decompression illness that was occurring in ichthyosarians. These aquatic creatures would have evolved an autonomic reflex to exhale while rapidly ascending and would not experience this type of decompression illness. I guess Hayman deserves credit for positing that it was the second type of decompression, but really this was low-hanging fruit. And a great big raspberry to Phys.Org for using the phrase "Dinosaur bends" in the title of an article that was not about dinosaurs.

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