  Small three-dimensional strongly coupled clusters of charged particles in a
spherical confinement potential arrange themselves in nested concentric shells.
If the particles are immersed into a background plasma the interaction is
screened. The cluster shell configuration is known to be sensitive to the
screening strength. With increased screening an increased population of the
inner shell(s) is observed. Here, we present a detailed analysis of the ground
state shell configurations and configuration changes in a wide range of
screening parameters for clusters with particle numbers $N$ in the range of 11
to 60. We report three types of anomalous behaviors which are observed upon
increase of screening, at fixed $N$ or for an increase of $N$ at fixed
screening. The results are obtained by means of extensive first principle
molecular dynamics simulations.
