We report the identification, from a photometric, astrometric and spectroscopic study, of a massive white dwarf member of the nearby, approximately solar metalicity, Coma Berenices open star cluster (Melotte 111). We find the optical to near-IR energy distribution of WD1216+260 to be entirely consistent with that of an isolated DA and determine the effective temperature and surface gravity of this object to be $T_{rm eff}$=$15739^{+197}_{-196}$K and log $g$=$8.46^{+0.03}_{-0.02}$. We set tight limits on the mass of a putative cool companion, M$simgreat$0.036M$_{odot}$ (spatially unresolved) and M$simgreat$0.034M$_{odot}$, (spatially resolved and a$simless$2500AU). Based on the predictions of CO core, thick-H layer evolutionary models we determine the mass and cooling time of WD1216+260 to be M$_{rm WD}$=$0.90 pm0.04$M$_{odot}$ and $tau$$_{rm cool}$=$363^{+46}_{-41}$Myrs respectively. For an adopted cluster age of $tau$=500$pm$100Myrs we infer the mass of its progenitor star to be M$_{rm init}$=$4.77^{+5.37}_{-0.97}$M$_{odot}$. We briefly discuss this result in the context of the form of the stellar initial mass-final mass relation.
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