75 million years ago, North America was divided into western and eastern halves of land by a shallow inland
Researchers have suggested that diversitymaintained by dividing territories and food sources. For example, horned dinosaurs (keratopsians) may have preferred coastal areas, while duckbill dinosaurs (hadrosaurs) lived mostly inland.
Until now, this hypothesis has remained unverified,because researchers cannot directly observe the behavior of dinosaurs and the state of ecosystems. To solve this riddle, a team of researchers compared the composition of stable isotopes in the fossil teeth of dinosaurs.
Stable isotopes- natural varieties of chemical elements(such as carbon or oxygen) that do not change over time into other elements. When animals consume food and water, stable isotopes of the elements that make up these resources are transferred into the animal's tissues, including tooth enamel.
Stable isotopic compositions of carbon and oxygenherbivorous dinosaurs have been measured using various methods. The main approaches are mass spectrometry and laser gas chromatography. The research was conducted at the Laboratory of Stable Isotopes in Western, with the participation of anthropology professor Fred Longstaff, researcher Lee Juan and project manager Thomas Cullen from the Field Museum.
“This approach allowed us to analyze verysmall samples and thereby extend the science of isotope ecology to dinosaur times, ”said Longstaff, a Canadian researcher in the field of stable isotopes. - As a rule, my work on isotope ecology is focused on animals of the ice age and the reasons for their extinction or survival. The attempt to go back to the time when the dinosaurs lived was both challenging and exciting. ”
Researchers compared measurement results forindividuals of each dinosaur species with other animals in this ancient ecosystem. It was found that the ranges of stable carbon and oxygen isotopes for large herbivorous dinosaurs strongly overlap, which is direct evidence refuting the hypothesis of using the habitat. That is, there were no distinguished regions for certain dinosaur species.
"Measurement of ratios of various isotopeselements such as carbon or oxygen in tooth enamel gives us a unique window into the animal’s diet and habitat, which has died out for millions of years, ”says Cullen. - Dinosaurs lived in a strange world: broad-leaved and flowering plants were much less common. In high latitudes it was warm enough to be comfortable even for crocodiles. The carbon dioxide content in the atmosphere was higher than today and there was almost no ice at the poles. ”
According to scientists, such a picture of the world is what humanity is striving for, having an anthropogenic impact on nature.
“It is very important that we understand how ecosystems and the environment function in such conditions so that we can better prepare for the future,” Cullen concluded.