Marine Reptiles Show Signs of the “Dinosaur” Bends

Marine reptiles and similar creatures might have sustained injuries from diving to great depths or swimming at great depths for too long. A study was completed on fossilized Ichthyosarians that brought attention to bone deformities that are consistent with bone deformities of humans suffering from decompression sickness, or “the bends”. The lesions were typical of those seen in humans who undergo changes in body pressure, which can cause the bends or a state of nitrogen narcosis. Nitrogen narcosis affects consciousness in a manner similar to alcohol intoxication. Links have been made between human “bends” and these Ichthyosarian bone deformities because human neck bones and the bones of prehistoric reptiles are very similar.

How the “Dinosaur” Bends Came About

An analysis by Associate Professor John Hayman of the University of Melbourne was published in Naturwissenschaften: Science of Nature. In his analysis, Associate Professor Hayman gives his thoughts on the cause of the deformities. His conclusions argue that the scarring may have been a result of deep diving and staying at great depths for too long, which can cause nitrogen to accumulate in the tissues of the body. As the Ichthyosarians ascended to the surface, nitrogen was released into the bloodstream in the form of bubbles because the body cannot hold the excess nitrogen at normal pressures. The nitrogen bubbles can expand and injure tissue, trigger clots, or block blood vessels in major organs. It was previously thought that quick ascents caused the lesions. Quick ascents still could have played a role though since the bends are affected by three things: the depth of dives, the duration of deep dives, and the speed of ascent. A long, deep dive requires a very slow ascent in order for nitrogen levels to naturally return to normal.

Were the “Dinosaur” Bends Worth it for Ithyosaurs?

Ichthyosarians may have realized some benefits to diving deeper for longer periods of time. Some potential benefits are an increased feeding range, more opportunities for thermoregulation, and a larger habitation zone. Whatever the benefits, they must have outweighed the maladies associated with decompression sickness. In humans this can cause joint pains, swollen or painful lymph nodes, itching and rashes, and pain in the torso, head, and neck area. It is also possible that the bends seen in Ichthyosarians were a result of hasty ascents to their oxygen supply. They may have swam deeper in search of food, then returned to the surface when oxygen supplies were depleted. Aquatic reptiles are more susceptible to the bends because their low oxygen consumption rate allows them to stay submerged for longer periods of time than mammals or birds.

How Did the Dinosaur Bends Affect Ichthyosaurs?

Associate Professor Hayman that the bends would not have affected the Ichthyosarians’ long-term survival, although detrimental conditions may have appeared late in their life spans. Decompression sickness is usually accompanied by fairly mild symptoms in humans and there is no reason to believe that Ichthyosarians would have suffered to a greater degree. The most common symptoms are joint pain and fatigue. These reptiles would still have been able to hunt for prey and reproduce—the two main goals of every creature in the animal kingdom despite suffering from the “dinosaur” bends.