We report evidence for a striking difference between S0 galaxies in the local field and in the Virgo Cluster .
While field S0 galaxies have disks whose surface-brightness profiles are roughly equally divided between the three main types ( Types I , II , and III : single-exponential , truncated , and antitruncated ) , Virgo S0s appear to be entirely lacking in disk truncations .
More specifically , the fraction of truncations in S0 galaxies with M _ { B } < -17 is 28 ^ { +7 } _ { -6 } % for the field , versus 0 ^ { +4 } _ { -0 } % for the Virgo Cluster galaxies ; the difference is significant at the 99.7 % level .
The discrepancy is made up almost entirely by Type I profiles , which are almost twice as frequent in the Virgo Cluster as they are in the field .

This suggests that S0 formation may be driven by different processes in cluster and field environments , and that outer-disk effects can be useful tests of S0 formation models .