A study by Melbourne University researcher Prof John Hayman shows that some ancient marine animals, including ichthyosaurs, giant dolphin-like reptiles that first appeared about 245 million years ago, may have injured themselves during deep-sea diving trips.
Earlier this year Dr Bruce Rothschild of the University of Kansas announced the discovery of bone deformities on the fossilized remains of ichthyosaurs. The lesions are 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.’ Prof Hayman’s study, published in the journal Naturwissenschaften, explains what may have caused these bone lesions.
The 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.
“Ichthyosaurs probably evolved the ability to dive deeper and to remain at depth for longer periods,” Prof 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 added.
Prof Hayman said the dangerous practice of deep sea diving wouldn’t have affected the reptiles’ long-term survival because any ill effects would have developed later in life.
“The lesions wouldn’t have been enough to kill the animal, and wouldn’t have affected its ability to hunt or breed.”
Prof Hayman said the new analysis was possible because structure of modern humans’ necks is very similar to the prehistoric reptiles.
“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,” the scientist concluded.
Bibliographic information: John Hayman. 2012. Deep-diving dinosaurs. Naturwissenschaften; vol. 99, no. 8, 671-672; doi: 10.1007/s00114-012-0937-x