  We present high-dispersion spectra of two extremely massive star clusters in
galactic merger remnants. One cluster, W30, is located in the ~500 Myr old
merger remnant NGC 7252 and has a velocity dispersion and effective radius of
sigma=27.5+-2.5 km/s and R_eff=9.3+-1.7 pc, respectively. The other cluster,
G114, located in the ~3 Gyr old merger remnant NGC 1316, is much more compact,
R_eff=4.08+-0.55 pc, and has a velocity dispersion of sigma=42.1+-2.8 km/s.
These measurements allow an estimate of the virial mass of the two clusters,
yielding M_dyn(W30)=1.59(+-0.26) * 10^7 Msun and M_dyn(G114)=1.64(+-0.13) *10^7
Msun. Both clusters are extremely massive, being more than three times heavier
than the most massive globular clusters in the Galaxy. For both clusters we
measure light-to-mass ratios, which when compared to simple stellar population
(SSP) models of the appropriate age, are consistent with a Kroupa-type stellar
mass function. Using measurements from the literature we find a strong age
dependence on how well SSP models (with underlying Kroupa or Salpeter-type
stellar mass functions) fit the light-to-mass ratio of clusters. Based on this
result we suggest that the large scatter in the light-to-mass ratio of the
youngest clusters is not due to variations in the underlying stellar mass
function, but instead to the rapidly changing internal dynamics of young
clusters. Finally, based on the positions of old globular clusters, young
massive clusters (YMCs), ultra-compact dwarf galaxies (UCDs) and dwarf-globular
transition objects (DGTOs) in kappa-space we conclude that 1) UCDs and DGTOs
are consistent with the high mass end of star clusters and 2) YMCs occupy a
much larger parameter space than old globular clusters, consistent with the
idea of preferential disruption of star clusters. (abridged)
