  Massive quiescent galaxies at z>1 have been found to have small physical
sizes, hence to be superdense. Several mechanisms, including minor mergers,
have been proposed for increasing galaxy sizes from high- to low-z. We search
for superdense massive galaxies in the WIde-field Nearby Galaxy-cluster Survey
(WINGS) of X-ray selected galaxy clusters at 0.04<z<0.07. We discover a
significant population of superdense massive galaxies with masses and sizes
comparable to those observed at high redshift. They approximately represent 22%
of all cluster galaxies more massive than 3x10^10Msol, are mostly S0 galaxies,
have a median effective radius <Re> =1.61+/-0.29kpc, a median Sersic index <n>
= 3.0+/-0.6, and very old stellar populations with a median mass-weighted age
of 12.1+/-1.3Gyr. We calculate a number density of 2.9x10^-2Mpc^-3 for
superdense galaxies in local clusters, and a hard lower limit of
1.3x10^-5Mpc^-3 in the whole comoving volume between z = 0.04 and z = 0.07. We
find a relation between mass, effective radius and luminosity-weighted age in
our cluster galaxies, which can mimic the claimed evolution of the radius with
redshift, if not properly taken into account. We compare our data with
spectroscopic high-z surveys and find that -when stellar masses are considered-
there is consistency with the local WINGS galaxy sizes out to z~2, while a
discrepancy of a factor of 3 exists with the only spectroscopic z>2 study. In
contrast, there is strong evidence for a large evolution in radius for the most
massive galaxies with M*>4x10^11Msol compared to similarly massive galaxies in
WINGS, i.e. the BCGs.
