Measured galaxy abundances compared with predicted [Si/Fe] and [Mg/Fe] yields from SN models as a function of progenitor mass and metallicity. As in Fig. 2, circles indicate CCSNe, squares HNe, and diamonds PISNe. Symbol colours indicate metallicity from Z = 0 (black) to Z = 0.05 (light grey). The shaded bands show the 68% credible intervals of the inferred abundances for NGC 1277 (pink) and the massive ETG sample (cyan), with solid lines marking the corresponding posterior medians. While the [Mg/Fe] abundance is broadly consistent with several enrichment channels, the high [Si/Fe] inferred for NGC 1277 is best matched, within the adopted yield grid, by very massive, metal-poor progenitors, including PISN models.