"We do not want to negate the influence of oxygen for the evolution of life in general with our study, but the gigantism of dinosaurs cannot be explained by those theories," said Ralf Tappert of the University of Innsbruck and lead author of the amber study, published in the journal Geochimica et Cosmochimica Acta, in a press release.
Amber and non-fossilized tree resins trapped a record of changing oxygen levels because sap-oozing trees intake of carbon dioxide changed depending on oxygen concentration. When oxygen levels changed, the trees collected different amounts of a form of carbon, an isotope known as carbon-13.
ANALYSIS: Redwoods Record Ancient Ocean Climate
During the dinosaur era, volcanic activity may have increased the amount of carbon dioxide in the air. This increased the greenhouse effect, which subsequently increased oxidative weathering, or the amount of oxygen bound to other chemicals during the weathering of rocks, according to the study.
IMAGE: Oligocene-era gecko trapped in amber. (PG Palmer, Wikimedia Commons)