Dinosaur life will help humanity know its future, Western researchers say. In order to survive and not conflict with each other, small and large representatives of ancient reptiles divided territories. But was it really so? Scientists write about this in the journal Geology.
75 million years ago, North America was divided into western and eastern parts of the land by a shallow inland sea. At the same time, the western part of the mainland was home to an extremely rich variety of dinosaurs. Scientists for a long time could not understand how exactly so many large animals coexisted in such a small area.
Researchers have suggested that diversity was maintained through the separation of 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, since 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 are natural types of chemical elements (such as carbon or oxygen) that do not turn into other elements over time. When animals consume food and water, the stable isotopes of the elements that make up these resources are transferred to animal tissue, including tooth enamel.
Stable isotopic compositions of carbon and oxygen of herbivorous dinosaurs were measured using various methods. The main approaches are mass spectrometry and laser gas chromatography. The studies were conducted at the Laboratory of Stable Isotopes in Western, with the participation of professor of anthropology Fred Longstaff, researcher Lee Juan and project manager Thomas Cullen from the Field Museum.
“This approach allowed us to analyze very small samples and thereby extend the science of isotope ecology to the time of the dinosaurs”, 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 the measurement results for individuals 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.
“Measuring the ratios of various isotopes of elements, 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.