Toothy-thermometers take dino's temperature for the first time
Dinosaur teeth turn out to be excellent thermometers, claim scientists in an upcoming paper in the latest Science, just published today. And they may hold the key to settling a decades-old controversy over the giants of the Jurassic. Were they slaves to the sun, needing heat from their surrounds to power up - like lizards and snakes? Or were they nimble and warm-blooded, like mammals and birds, living fast on energy from a high metabolism? The answer implies very different lifestyles choices for these most-famous of our prehistoric inhabitants.
Turning to dino-dentures, and specifically the enamel of their teeth, for help on the hot vs cold debate, came about because of previous work done at the California Institute of Technology. A technique pioneered there, by John Eiler and Robert Eagle, looked to the isotopic composition of oxygen and carbon in a mineral found in enamel ---– bio-apatite ---– for temperature clues. This enabled them to pin-down the body temperatures of 30,000 year-old mammoths and 12-million year old rhinoceroses.
The carbonate found in apatite contains very small numbers of 'heavy' versions (isotopes) of the atoms that form it ---– the isotopes carbon-13 and oxygen-18. Critically, the clumping of these two rare isotopes, into a common bond, depends on the temperature when the mineral was formed. So measuring these isotopes can give you the temperature in the mouth of the creature being sampled.
Amazingly, traces of original bio-apatite are still to be found in well-preserved dinosaur teeth hundreds of millions years-old. With careful selection and preparation, the team was able to isolate and test the teeth of two dinosaurs species ---– massive plant-eating sauropods, Brachiosaurus, and Camarasaurus, which stomped across the Jurassic plains 150 million years ago. Sixteen teeth were tested in all, dug up in Wyoming, Oklahoma and in Tanzania, in Africa.
The team found that the toothy-thermometers read 100 degrees Fahrenheit (38°C) for the monstrous Brachiosaurus, and a cooler 96°F (36°C) for the smaller Camarasaurus. That's much warmer than for modern reptiles, though a shade cooler than the typical body temperature of birds. So does this mean prove conclusively that dinosaurs are warm-blooded? Unfortunately not.
That's because the two dinosaur species tested are so huge, that they'd be able to maintain a relatively warm temperature, even without burning energy, as warm-blooded mammals and birds do. "If you're an animal that you can approximate as a sphere of meat the size of a room, you can't be cold unless you're dead," said Eiler. But now that the technique has been proven, the next step is to move onto the more challenging smaller and younger dinosaurs.
If these still show a relatively high body-temperature, the case for warm-blooded dinosaurs would be considerably strengthened. 'The consensus was that no one would ever measure dinosaur body temperatures, that it's impossible to do,' said John Eiler. 'Nobody has used this approach to look at dinosaur body temperatures before, so our study provides a completely different angle on the longstanding debate about dinosaur physiology.' The story of the dinosaurs may just be about to be rewritten.
Top Image: Caption: This is a Jurassic sauropod. Credit: Illustrated by Russell Hawley, Tate Geological Museum