Shrinking dinosaurs and the evolution of endothermy in birds
(PHYSorg.com Archaeology & Fossils)

The evolution of endothermy (thermoregulation by metabolic means) represents a major transition in vertebrate history. However, the process of endothermy evolution and its timeline in birds and mammals remains controversial. In a new report on Science Advances, Enrico L. Rezende and a team of researchers at the Center of Applied Ecology and Sustainability, and the Institute of Environmental and Evolutionary Sciences in Chile, combined a heat transfer model with theropod body size data. The researchers then reconstructed the evolution of metabolic rates along the bird stem lineage. The results suggested that a reduction in size constituted the path of least resistance for endothermy to evolve-maximizing thermal niche expansion, while reducing costs of elevated energy requirements.