Oh yeah, this blog is awesome for cool sciency stuff presented in an easy-to-digest format. http://blogs.discovermagazine.com/notrocketscience
One of the latest posts is this: Prehistoric sea dragons kept themselves warm
When dinosaurs ruled the land, other groups of prehistoric reptiles dominated the waters. Their bones have also fossilised and they reveal much about how these ‘sea dragons’ lived. They tell us about the shape of their bodies, the things they ate and even how they determined their sex. And according to Aurélien Bernard from the University of Lyon, they can tell us whether these reptiles could control their body temperature.
The majority of reptiles are ‘cold-blooded’. Unlike mammals and birds, they can’t generate and retain their own heat, and their body temperature depends on their surroundings. But Bernard thinks that at three groups of marine reptiles – the dolphin-shaped ichthyosaurs, the crocodile-shaped mosasaurs, and the the paddle-flippered plesiosaurs – bucked this trend. Whether in tropical or cold waters, they could maintain a constant body temperature that reached as high as 35-39 degrees Celsius.
Bernard estimated the body temperature of these ocean-going predators by studying their teeth. He took samples from 40 plesiosaurs, ichthyosaurs and mosasaurs as well as several prehistoric fish. The specimens came from five continents, and a range of periods from the Triassic to the Cretaceous. In every tooth, he measured the amount of different oxygen isotopes, a value that depends on the animal’s body temperature and the composition of the water it swallows.
The data from the fish helped to calibrate the reptile data. By and large, fish body temperatures reflect the temperatures of the surrounding seawater. If the reptiles’ teeth had the same composition of oxygen isotopes as those of the fish, their bodies were also similarly as warm as their surroundings and they were probably cold-blooded. Any differences reflect a different means of regulating body heat.
Using a mathematical model, Bernard calculated that both ichthyosaurs and plesiosaurs managed to keep a constant balmy body temperature from around 24-35°C, even when swimming through waters as cold as 12°C. The abilities of mosasaurs were less clear, but it seems that they had at least some control over their body temperature.
These results fit with the portraits of ichthyosaurs and plesiosaurs as active, fast-swimming hunters, which needed warm bodies for their fast chases and deep dives. Likewise, the ambiguity around the body temperature of mosasaurs is consistent with the idea that they were ambush predators, whose sit-and-wait strategies wouldn’t have demanded such high metabolisms.
So ancient critters we thought were reptiles appear to have evolved an exothermic metabolism (wot are a sciency thing that means they had warm blood like mammals). This is sorta surprising. Mind you there is evidence that a lot of dinosaurs were warm-blooded too, particularly theropods (which modern birds came from).