Bones can tell you a lot about a creature, but there's much more they can't tell you. Bones are not behavior. We know what the skeletons of dinosaurs looked like. But there's a great deal about their appearance and behavior that we can only guess at.
Sometimes, though, bones can surprise you. Sometimes, they carry secrets locked inside. At Not Exactly Rocket Science, Ed Yong writes about a new study that's uncovered evidence about dinosaur behavior, using information stored in the dinosaurs' teeth. The paper suggests that the North American Camarasaurus had a seasonal migration.
Reptiles replace their teeth throughout their lives and the dinosaurs would have been no different. Whenever they drank, they incorporated oxygen atoms from the water into the enamel of their growing teeth. Different bodies of water contain different mixes of oxygen isotopes, and the dinosaurs' enamel records a history of these blends. They were what they drank.
It's easy enough to measure the levels of oxygen isotopes in dinosaur teeth, but you need something to compare that against. How could anyone possibly discern the levels of such isotopes in bodies of water that existed millions of years ago? Local rocks provide the answer. The oxygen also fuelled the growth of minerals like calcium carbonate (limestone), which preserve these ancient atoms just as dinosaur teeth do. If dinosaur enamel contains a different blend of oxygen to the surrounding carbonates, the place where the animal drank must be somewhere different from the place where it died.
Palaeontologists have used oxygen isotopes to infer all manner of dinosaur traits, from the fish-eating habits of spinosaurs to the hot body temperatures of sauropods to the chilly conditions endured by Chinese dinosaurs. These atoms have acted as menus and thermometers. Now, Fricke has turned them into maps.