The optical rest–frame sizes of 10 of the most massive ( \sim 5 \times 10 ^ { 11 } h _ { 70 } ^ { -2 } M _ { \sun } ) galaxies found in the near–infrared MUNICS survey at 1.2 < z < 1.7 are analysed .
Sizes were estimated both in the J and K ’ filters .
These massive galaxies are at least a factor of 4 _ { -1.0 } ^ { +1.9 } ( \pm 1 \sigma ) smaller in the rest–frame V–band than local counterparts of the same stellar mass .
Consequently , the stellar mass density of these objects is ( at least ) 60 times larger than massive ellipticals today .
Although the stellar populations of these objects are passively fading , their structural properties are rapidly changing since that redshift .
This observational fact disagrees with a scenario where the more massive and passive galaxies are fully assembled at z \sim 1.4 ( i.e .
a monolithic scenario ) and points towards a dry merger scenario as the responsible mechanism for the subsequent evolution of these galaxies .