A the allometric coefficient in six groups of endothermic animals, depending on the geological time of divergence of the clades: by the phylogenetic generalised least squares (PGLS) and ordinary least squares (OLS). a (mlO2/h) is the allometric coefficient (antilog of the regression intercept) B the exponents in six groups of endothermic animals, depending on the geological time of divergence of the clades: by the phylogenetic generalised least squares (PGLS) and ordinary least squares (OLS). b is a scaling exponent (the slope of the regression line).