Warm-Blooded Sea Monsters of the Mesozoic

Origami Plesiosaurus by Oriholic Jared, via Flickr.

A new study published in Science suggests that the great predators of Mesozoic seas, the plesiosaurs, icthyosaurs, and mosasaurs, maintained an average body temperature around 100 degrees Fahrenheit. This conclusion was achieved by studying the oxygen isotopes in their teeth; fish from the mesozoic and today - all cold-blooded, of course - show variation in their oxygen isotopes based on the temperature of water they live in. The marine reptiles of the Mesozoic don't show this variation. No matter what temperature water they lived in, they maintained a constant temperature and thus can be assumed to have been active predators adept at cornering the apex predator niche in all sorts of marine environments.

It's important to note that this doesn't directly relate to the metabolism of dinosaurs, which were distant cousins of the aquatic reptiles. But it is another demonstration that the "slow, sluggish, cold-blooded" baggage associated with the word "reptile" only hides the stunning diversity of adaptations these critters have employed over their hundreds of millions of years on Earth.