Age-metallicity relation (AMR) for 82 GCs (black dots) analysed by Massari et al. (2019) (plot based on their Fig. 4). The ages are taken from Vandenberg et al. (2013) and the metallicities from Carretta et al. (2009b). In each panel, one progenitor is highlighted. From top to bottom: First panel, main-progenitor (disc and bulge); second panel, low energy; third panel, Gaia-Enceladus. The magenta square represents Pal 6 with metallicity and age of the present work.