  We present a short review of our results on the collectivity and the
suppression pattern of charmed mesons in heavy-ion collisions based on the
microscopic Hadron-String Dynamics (HSD) transport approach for different
scenarios of charm interactions with the surrounding matter - the 'comover'
dissociation by mesons with further recreation by D+Dbar channels and
'pre-hadronic' interaction scenarios. While at SPS energies the hadronic
'comover' absorption scenario is found to be compatible with the experimental
data, the dynamics of c and cbar quarks at RHIC are dominated by partonic or
'pre-hadronic' interactions in the strongly coupled quark-gluon plasma stage
and cannot be modeled by pure hadronic interactions. We find that the
collective flow of charm in the purely hadronic scenario appears compatible
with the data at SPS energies but underestimates the data at top RHIC energies.
Thus, the large elliptic flow v2 of D mesons and the low R_AA(pT) of J/Psi seen
experimentally at RHIC have to be attributed to early interactions of
non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic
interactions are mandatory in order to describe the narrowing of the J/Psi
rapidity distribution from p+p to central Au+Au collisions at the top RHIC
energy. We demonstrate additionally that the strong quenching of high-pT
J/Psi's in central Au+Au collisions indicates that a fraction of final J/Psi
mesons is created by a coalescence mechanism close to the phase boundary.
