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Monday, April 23, 2012

Jurassic marine reptiles did not explode



Here’s a question you’ve probably never asked yourself: did extinct marine reptiles regularly explode after death? Thanks to the efforts of Achim Reisdorf of Universit├Ąt Basel and his colleagues, you can rest assured that the answer is no.

The exploding reptile hypothesis was based upon the fact that the fossil remains of marine tetrapods known as ichthyosaurs are often found ‘disarticulated’. That is, they seem to have suffered from some sort of internal disruption. For example, female ichythosaurs have been found with embryos scattered around outside their bodies.

 

Ichthyosaur female with scattered embryos outside of the body of the mother.
Credit: UZH.

The idea of dead animals exploding isn’t as far fetched as it sounds. Intestinal bacteria can quickly bloat carcasses with putrefying gases to the point where any stress on the skin can result in an explosion of fluid and even internal organs. The authors include some vivid imagery of people running from an exploding whale that someone had the misjudgment to prod too abruptly.

An important point to remember is that the whale in question was located on the shore. At depth, the pressure of the water would have been great enough to prevent any such explosion. The authors calculated that the amount of intestinal pressure within decaying ichythosaurs could not have overcome the water pressure at the depth at which they were found. Therefore, the reptiles could not have exploded.

So what did cause the ribs and embryos to be strewn about? One possibility is that sediments crushed the bodies, and then currents moved the incompletely buried pieces about.