Sea Monsters: A Toothy Issue

More leviathans came to the attention of Triple P when I found this article from Scientific America last week. It is about the debate over dinosaurs of the sea and whether or not they might have been warm blooded.

Evidently the dolphin-like ichthyosaur whose skeleton is shown above, along with plesiosaurs and smaller mosasaurs may have been able to regulate their own temperatures to some degree. The process by which they would do that could have been similar to the one used by some modern tuna and sharks. These animals are homeothermic, meaning that they are not "warm blooded" as mammals are but their body temperature does stay relatively high and consistent. On the other hand, researches speculate the prehistoric animals may have been gigantothermic, like leatherback turtles. In such cases the animal's large body mass allows it to stay warm.

The study, led by Aurelien Bernard of the University of Lyon, France, was published online June 10th. The researchers evaluated oxygen isotopes in the teeth of the extinct creatures and compared them with isotope levels in fossil fish found near them. In this way, Bernard's team determined that the Mesozoic sea creatures' body temperatures may have hovered around 100 degrees or 39 Celsius.

There is debate over that finding, however. Ryosuke Motani of the University of California, Davis believes that those temperatures are too high. Factoring in what he calls "time dependent depletion" of oxygen isotopes, Motani figures the animals' body temperatures were more like 85 degrees or 26 Celsius. This is more in line with modern tuna and turtles.

Either way, the benefit to the ichthyosaurs was in where they could hunt. Warmer bodies meant the ability to "cruise" for fish in colder waters. The benefit to science is one of long term study. As Motani indicates in the article, the research gives scientists a "rare opportunity to clarify environmental effects on evolution." And that is timely indeed.