Evolution of the median circularity parameter ϵ for stars born in the cold disc that populate the warm disc at z = 0 (orange lines) and for stars born in the cold disc that remained there until the present time (red lines). The figure also shows the presence of satellites with mass ratios ≥3% (light grey: within 0.5R₂₀₀ and dark grey within 0.3R₂₀₀), as well as galaxies that developed bars: downward green arrows correspond to bars identified by Fragkoudi et al. (2025) and upward purple arrows to López et al. (2025) which additionally developed boxy-peanut bulges.