  Pseudo-bulges are expected to markedly differ from classical,
quasi-monolithically forming bulges in their star formation history (SFH) and
chemical abundance patterns. To test this simple expectation, we carry out a
comparative structural and spectral synthesis analysis of 106 red, massive
galaxies issued from the SDSS, subdivided into bulgeless, pseudo-bulge and
classical bulge galaxies according to their photometric characteristics, and
further obeying a specific selection to minimize uncertainties in the analysis
and ensure an unbiased derivation and comparison of SFHs. Our 2D photometry
analysis suggests that disks underlying pseudo-bulges typically have larger
exponential scale lengths than bulgeless galaxies, despite similar integral
disk luminosities. Spectral synthesis models of the stellar emission within the
3" SDSS fiber aperture reveal a clear segregation of bulgeless and pseudo-bulge
galaxies from classical bulges on the luminosity-weighted planes of
age-metallicity and mass-metallicity, though a large dispersion is observed
within the two former classes. The secular growth of pseudo-bulges is also
reflected upon their cumulative stellar mass as a function of time, which is
shallower than that for classical bulges. Such results suggest that the centers
of bulgeless and pseudo-bulge galaxies substantially differ from those of bulgy
galaxies with respect to their SFH and chemical enrichment history, which
likely points to different formation/assembly mechanisms.
