Panel (a) displays the distributions of the Sérsic index for ETGs and LTGs. The gray dashed line marks the classification threshold at n = 2.5. Panel (b) shows the distribution in the G–M₂₀ plane for galaxies classified as ETGs and LTGs. The contour levels enclose 20%, 50%, and 80% of the respective subclass, from the innermost to the outermost regions. The dashed line, given by G = 0.14M₂₀ + 0.80 (J. M. Lotz et al. 2008), represents the boundary between LTGs and ETGs.