  To provide a quantitative cosmological context to ongoing observational work
on the formation histories and location of compact massive galaxies, we locate
and study a sample of exceptionally compact systems in the Bolshoi simulation,
using the dark matter structural parameters from a real, compact massive galaxy
(NGC 1277) as a basis for our working criteria. We find that over 80% of
objects in this nominal compact category are substructures of more massive
groups or clusters, and that the probability of a given massive substructure
being this compact increases significantly with the mass of the host structure;
rising to ~30% for the most massive clusters in the simulation. Tracking the
main progenitors of this subsample back to z=2, we find them all to be distinct
structures with scale radii and densities representative of the population as a
whole at this epoch. What does characterise their histories, in addition to
mostly becoming substructures, is that they have almost all experienced
below-average mass accretion since z=2; a third of them barely retaining, or
even losing mass during the intervening 10 Gyr.
