Morphology mix of massive galaxies in the probed cluster regions and in the reference field at 1.3 < z < 1.8. Left panel: fraction of log(M/M_⊙) > 10.85 cluster galaxies with Sersic indices n ≤ 1.5, 1.5 < n < 2.5 and n ≥ 2.5 (dark grey symbols), and the corresponding fractions for the field reference sample (grey bars). For clarity, error bars (binomial, Cameron 2011) are only shown for cluster samples. Right panel: analogous fractions for the quiescent and star-forming populations, as indicated. Solid (empty) symbols refer to cluster galaxy samples excluding (including) sources within ±0.1 mag around the quiescent vs. star-forming classification border. Solid (hatched) bars analogously refer to the corresponding field reference samples.