Taking extinct animals’ temperatures

Were the dinosaurs warm blooded or cold blooded? Thanks to scientists from Caltech, UCLA, Universität Bonn and the University of Florida, we’re close to having that answer. They’ve discovered a way to reliably take the internal temperature of fossilized animals.

The trick was to look for clusters of the isotopes carbon-13 (¹³C) and oxygen-18 (¹⁸O). As new bone is created in living vertebrates, carbon and oxygen (among other elements) precipitate out of the bloodstream and harden into bioapatite, or mineralized bone. A fraction of the carbon and oxygen will be ¹³C and ¹⁸O. Now here’s the interesting part: those two isotopes will be clumped together if they were deposited at lower temperatures, but spread more randomly through the bioapatite if they were deposited at higher temperatures.

The scientists have tested their concept by looking at the bioapatite of living animals. They then examined the teeth of mammoths and extinct rhinos (mammals with a high internal temperature) and an extinct relative of the alligator (a reptile with a low internal temperature). Thus far, the isotope clumping data correlates well with the expected internal temperatures of the animals.

The researchers plan to start examining dinosaur eggshells and teeth next. Aside from learning some interesting things about dinosaurs, the new data could yield important information about the evolution of birds.

As John Eiler of Caltech says:

Were [birds] warm-blooded before or after they started to fly? Before or after they developed feathers?

Eiler and his colleagues are eager to answer those questions.