  We present a detailed analysis of the evolution of the rest-frame B-band
morphology of K-selected galaxies with 0 < z < 2.5. This work is based on the
K20 spectroscopic sample (Ks<20) located within the Chandra Deep Field South
area, coupled with the public deep GOODS HST+ACSmulti-band optical imaging
available in that field. Thanks to the spectroscopic completeness of this
catalog reaching 94%, we can compare the morphological and spectroscopic
properties of galaxies with unprecedented detail. Our morphological analysis
includes visual inspection and automatic procedures using both parametric (e.g.
the Sersic indices treated by the GALFIT and GASPHOT packages) and
non-parametric (the Concentration, Asymmetry and clumpineSs, CAS) methods. Our
analysis classifies the K20 galaxies as: 60/300 (20%, class 1) normal
ellipticals/S0; 14/300 (4%, class 2) perturbed or peculiar ellipticals; 80/300
(27%, class 3) normal spirals; 48/300 (16%, class 4) perturbed or actively
star-forming spirals; 98/300 (33%, class 5) irregulars. The evolution of the
merging fraction is constrained up to z~2, by carefully accounting effects of
morphological k-correction: both asymmetry criterion and pair statistic show an
increasing merging fraction as a function of the redshift. We finally analyse
the redshift-dependence of the effective radii for early- and late-type
galaxies and find some mild evidence for a decrease with z of the early-type
galaxy sizes, while disks and irregulars remain constant. Altogether, this
analysis of the K20 sample indicates the large predominance of spirals and
irregulars at 0.5<z<1.5 in K-band selected samples at even moderate depths.
