  We present a high signal to noise (S/N$>$10) medium resolution (R=2000)
LBT-LUCIFER spectrum of the early-type galaxy (ETG) S2F1-142 at $z\simeq1.4$.
By means of the CaT line at $8662$ \AA, we measured its redshift $z=1.386\pm
0.001$ and we estimated its velocity dispersion $\sigma_{v}=340 ^{-60}_{+120}$
km/s. Its corresponding virial mass is 3.9$\times10^{11}$ M$_\odot$, compatible
with the stellar mass estimates obtained assuming Initial Mass Functions (IMFs)
less dwarf rich than the Salpeter one. S2F1-142 is a compact galaxy with
$R_{e}$=3.1$\pm$0.2 kpc, i.e., an effective radius more than three times
smaller than the average $R_{e}$ of early-type galaxies with the same mass in
the local universe. At the same time, we found local and high redshift galaxies
with a similar mass content and similar effective radius confirming that it is
fully consistent with the already available measures of $R_{e}$ and
$\sigma_{v}$ both in the local and in the distant universe. Considering the
distribution of $R_{e}$ and $\sigma_{v}$ as a function of the stellar mass
content of ETGs, both in the local and in the distant universe, we noticed that
the measured velocity dispersions of the more compact galaxies are on average
slightly lower than expected on the basis of their compactness and the virial
theorem, suggesting that {\it i)} their dark matter content is lower than in
the more diffuse galaxies and/or {\it ii)} their luminosity profiles are
steeper than in the more diffuse galaxies and/or {\it iii)} their larger
compactness is an apparent effect caused by the overestimate of their stellar
mass content (due to bottom lighter IMF and/or systematic affecting the stellar
mass estimates).
