Finite temperature lattice simulations of quantum chromodynamics (QCD) are
sensitive to the hadronic mass spectrum for temperatures below the "critical"
temperature T_c ~ 160 MeV. We show that a recent precision determination of the
QCD trace anomaly shows evidence for the existence of a large number of hadron
states beyond those known from experiment. The lattice results are well
represented by an exponentially growing hadron mass spectrum up to a
temperature T = 155 MeV. Using simple parametrizations we show how one may
estimate the total spectral weight in these yet undermined states
