K is for Cretaceous
Cretaceous starts with a ‘C,’ so why is it K for Cretaceous? All the divisions of the Earth’s geological time scale have one- or two-letter designations, kind of like all the elements of the periodic table have a symbol (like C for carbon or Au for gold). The abbreviation for Cretaceous is K, from the German for chalk (kreide) and also because ‘C’ is also already used for Carboniferous.
For today’s installment, we’ll look a paper that utilizes stable oxygen isotopes from the teeth of a dinosaur to determine how fast the teeth grown.
Suarez, You, Suarez, Li, and Treischmann, 2017, Stable isotopes reveal rapid enamel elongation (amelogenesis) rates for the early Cretaceous iguanodontial dinosaur Lanzhousaruus magnidens, Nature Scientific Reports, v. 7: 15319 | DOI:10.1038/s41598-017-15653-6
Iguanodontians were herbivorous dinosaurs with tightly packed teeth optimized for chewing vegetation. These dinosaurs replaced their teeth continuously though life so that their chewing mechanism was always ready to go.
Lanzhousaurus magnidens only has 14 teeth in each quadrant of its mouth. These teeth were really big. The question the researchers wanted to explore was just how fast would these teeth need to grow so that the jaws were always ready to chew.
With isotopic analysis, it is possible to determine how quickly teeth elongate as they grow. Oxygen isotopes vary with seasons (mostly because of temperature changes) and this is recorded in the tooth incrementally as the tooth grow. When multiple samples are taken along the length of a tooth, seasonal changes can be seen and the rate of tooth growth can be determined.