The fossil of a pregnant ichthyosaur, whose embryos were found scattered around it, has bewildered paleontologists as to how such a thing could happen. One theory is that the creature exploded, but new research in decomposing humans says otherwise.
The fossil is estimated to be 182 million years old, embedded in rock that was once the ocean floor in Holzmaden, Germany. With the mother's skeleton in very good condition, yet her 10 embryos being found outside of her body, a long held theory since the mid-1970s has been that the bloated ichthyosaur must have exploded after death and shot out the embryos.
The process of putrefaction, or rotting, would be to blame in that scenario. In this case, gasses released from the rotting tissue would have built up immense pressure inside the animal, resulting in an explosion that would have spread the ichthyosaur's inners around it as it sunk to the seabed.
Ichthyosaurs dominated the oceans from 245 to 90 million years ago, abundant in the Jurassic period. Though not a true dinosaur itself, ichthyosaur was a close relative to the dinosaurs that evolved from a common ancestor back into the sea, much in the same way that whales evolved from land mammals.
A study in Frankurt was done that examined decomposing large-lunged marine mammals, as well as over 100 human corpses in differing stages of bloating, to better understand the temperatures and pressures that build up after an animal dies. The measurements were collected using a tool known as a manometer.
The scientists concluded that the pressure needed to burst the ichthyosaur could very likely not have been produced. They measured an average pressure of only 0.035 bar created by the gasses inside the abdomens of their bloated test subjects. 1 bar is about the same as the air pressure of Earth at sea level. Meanwhile, an astonishing 15 bars would have to be achieved for the animal to explode, scattering the bones in the process.
"Large vertebrates that decompose cannot act as natural explosive charges. Our results can be extended to lung-breathing vertebrates in general.", says paleontologist Christian Klug.
The February 1 journal of Palaeobiodiversity and Palaeoenvironments goes on: "Our data and a review of the literature demonstrate that carcasses sink and do not explode (and spread skeletal elements),"
Ichthyosaurs dominated the oceans from 245 to 90 million years ago, abundant in the Jurassic period.
That does leave the question of how exactly the embryos could have gotten outside of the mother ichthyosaur in the first place, however.
Researchers now theorise that the ichthyosaur simply sank to the bottom after death, at a depth of about 150 meters (492 feet), and the combination of decomposition and gentle currents washed the embryos to lay outside of her skeleton. Not quite as dramatic as an explosion would be, but it's a sound conclusion nonetheless. Especially given that the remains did not fall victim to scavengers, and water pressures kept the body intact on the seabed, it truly remains a remarkable find.